


Book. 



Copyright )) 0 


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COPYRIGHT DEPOSm 
















J 


Field Fortification 


A study of the 
Western Front in Europe 
1914-1916 


Reprinted from the 
Infantry Journal 

1917 


WASHINGTON 

THE UNITED STATES INFANTRY ASSOCIATION 

19 17 



Copyright 1917 

The U. S. Infantry Association ' 



S£P 15 ISIy 



©CI.A473606 ^ 



PREFACE 


This treatise is based on authentic information from the Western front in 
Europe, but the art and practice of Field Fortification today is like so many other 
things, in the melting pot, and men who study this work may find, upon their 
arrival in France that certain methods have been changed; or, what is perhaps 
more probable, that new methods have been adopted in addition to those set forth. 

For example, there is a growing tendency on the part of our enemy to develop 
centers of resistance rather than continuous lines. In spite of this constant 
change and development, the general principles, and probably most of the practice 
here set forth, will be found in application where the forces of the United States 
are now in training to fight. A manual of this kind is,- however, like a technical 
dictionary. You buy the last one obtainable and should not expect words and 
descriptions of processes which have come into use after the date of publication; 
the others still hold good, or most of them still hold good. The editor with the 
best intentions in the world cannot see just what tomorrow will bring forth. 

It is accordingly hoped that this manual will be found useful in the primary 
military education which the soldiers of the United States are preparing them¬ 
selves to continue in France and to complete in Germany, the home of technical 
training. 



CONTEXTS 


Page 

Chapter 1. 7 

General principles and classes of devices of field fortification. Role of fortification 
on the western front. Use of field fortifications on the offensive and on the defensive. 
Thickness for defense against fire of infantry, artillery and trench weapons. Intrenching 
tools for infantry, cavalry’ and engineers. 

Chapter II. 17 

Utilizing natural cover, profiles and execution of light field fortifications. Infantry. 
Concealment and protection. Individual organization of natural cover. General 
organization of natural cover. Organization of artificial intrenchments. Types of 
light field fortifications. Trace of intrenchments. Construction of trenches. 


Chapter III.32 

Trench weapons. Hand grenades, rifle grenades, and trench weapons. Principles of the 
fire of trench weapons. Destruction of unexploded grenades. Conclusion. 

Chapter IV. 42 


Profile and execution of deliberate field works. Increase of resistance of trenches to 
artillery fire. Protection for the personnel in the immediate vicinity of the firing trench. 
Protection of the personnel in rear of the first lines. Construction of sheltered com¬ 
munications. Construction of shelters for observation. Illumination and communica¬ 
tion. Depots for material, ammunition and arms. Emplacements and shelters for 
machine guns and trench weapons. Improving living conditions in the trenches. 
Conclusion. 

Chapter V.75 

Organization of intrenched zones. Trace of the firing line. Element of platoon or 
section trench and group of elements of trench. Plan for organization of supporting 
point. Defensive organization of a sector. Organization of the second and third 
intrenched zones. Distribution of troops. Special defensive organizations. Inhabited 
places, villages. Conclusion. 


* o 





























































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■ 


















CHAPTER I 


PART I. 

GENERAL PRINCIPLES AND CLASSES OF 
DEVICES OF FIELD FORTIFICATION. 

1. The power of modern armament 
(rapid fire rifles, automatic rifles, ma¬ 
chine guns, field guns, heavy field guns, 
and trench weapons) requires that 
troops, both on the offensive and de¬ 
fensive, constantly seek cover in order 
to avoid heavy losses. 

2. A trench is a shield that saves 
losses and increases the immediate de¬ 
fensive and the future offensive power 
of troops who know how to use it. It 
permits infantry to halt in safety under 
fire, in order to continue the advance 
when a favorable opportunity offers. 
Under penalty of complete destruction, 
it is absolutely necessary for attacking 
troops to shelter themselves when under 
fire, and to fortify, step by step, the 
ground won. Troops that cannot reach 
the enemy by an uninterrupted advance 
are enabled to stop and prepare for the 
next advance by means of the fortifica¬ 
tion of the terrain. 

3. Field fortification likewise enables 
the offensive to engage the enemy, to 
hold him on one part of the front so as 
to concentrate forces and reserves, and 
strike him at another part of the front. 

4. The passive defense should be 
avoided. When troops have once dug 
themselves in. or organized supporting 
points, required by the tactical condi¬ 
tions existing, they must profit by their 
work and carry out the mission assigned 
them, by coordinating the action of the 
intrenched units with that of the units 
intended for the counter attack, which 


are protected by the natural features of 
the terrain. 

5. This preparation for an attack 
which may last weeks and months does 
not bring about immobility, but permits 
an economy of forces in certain places, 
and a concentration of strength in 
others, with a view to sudden and 
decisive action. 

6. The soldier properly instructed, 
disciplined, led and imbued with the 
principle that the offensive dominates 
all the actions of war and that it is the 
indispensable condition of success, will 
not hesitate any more to quit the trench 
than he would to leave a furrow or a 
road-side ditch in order to advance when 
ordered by his chief. Napoleon said: 
“ The trench is always useful, never 
harmful, when it is properly under¬ 
stood. To argue that victory belongs to 
the one who marches, advances, ma¬ 
noeuvres, and that it is unnecessary to 
work, is to talk lightly and foolishly.” 

7. The fortification of the battlefield 
includes the opening of communications, 
work to facilitate the movements of 
troops to the front and to improve their 
fire, demolitions on the front of fortified 
positions and in the rear of a column in 
retreat, illumination of the battlefield, 
obstacles, and finally, the means for pro¬ 
tection against these devices. 

8. The principal devices which permit 
the development of the maximum power 
of troops, and are the component ele¬ 
ments of all field fortification, are: 

First, cover, which protects against 
fire, while permitting a good use of fire¬ 
arms. 


7 


8 


Field Fortification 


Second, obstacles, which increase the 
power of a fortification by holding the 
enemy under fire of the defenders. 

Third, view, which permits the de¬ 
fenders to fire and to see what is going 
on. Artillery fire, especially, needs long 
and extended views; hence the neces¬ 
sity for having observing stations and 
for holding securely those points of the 
terrain which afford positions for them. 

Fourth, communications. These as¬ 
sure the rapid transmission of orders, 
rapid and sure movements of troops 
and material. 

PART II. 

ROEE OF FORTIFICATION ON THE WEST¬ 
ERN FRONT IN EUROPE, 1914-16. 

9. Before the superiority of numbers 
of the Germans (22 corps against 17), 
the position taken by the French on the 
front Sambre-et-Meuse on August 21, 
1914, was broken on the 23d. The Ger¬ 
mans had already made use of intrench- 
ments plentifully supplied with machine 
guns to break the French offensive. The 
retreat was effected in the center and 
left wing of the French army, while 
the right wing, resting on the Vosges 
and on the Meuse River, held fast and 
formed a pivot. This right wing em¬ 
ployed field fortification, both light and 
reinforced, to the fullest extent. It im¬ 
mediately abandoned the regulation 
types for deeper and narrower profiles. 

10. On September 5th, the order for 
the offensive was given. The French 
armies stood fast and dug in, and the 
Germans did likewise. But they still 
used the light form of fortification, util¬ 
izing at first rivers, streams, marshes, 
earth walls, cuts and fills of roads and 
railroads, reinforcing these natural ob¬ 
stacles by light intrenchments and sim¬ 


ple lines of barbed wire stretched 
through the growing crops. 

11. The French offensive succeeded 
and the Germans retreated. But the ex¬ 
haustion of the troops’ energy and am¬ 
munition became evident on both sides, 
and the slowness of the pursuit per¬ 
mitted the Germans to dig in and form 
on the right bank of the Aisne a forti¬ 
fied barrier, utilizing natural obstacles 
of the most diverse kinds to shelter and 
strengthen firing lines, to hide and pro¬ 
tect batteries of all calibers, to shelter 
reserves, and headquarters, and to re¬ 
organize supply in food and ammuni¬ 
tion. This barrier forms an extended 
front, an uninterrupted succession of 
supporting points, of centers of resist¬ 
ance, natural and artificial, mutually 
supporting each other, yet so disposed 
that the fall of one does not bring about 
the fall of others, the whole presenting 
a close analogy with the defensive or¬ 
ganization of a modern fortified place, 
with its advanced positions, its principal 
line of defense, its supporting positions 
and its central nucleus. 

PART III. 

USE OF FIEED FORTIFICATION ON THE 

OFFENSIVE AND ON THE DEFENSIVE. 

Use on the Offensive. 

12. In the preliminary operations, the 

Advance Guard has as its mis¬ 
sion : 

To clear away obstacles. 

To attack the enemy so as to 
oblige him to show his force. 

To occupy the supporting points 
necessary for the deployment of 
the main body, and if necessary 
to capture them. 

To organize supporting points. 



Field Fortification 


9 


13. During the approach, it is still the 

mission of the Advance Guard: 
To destroy obstacles. 

To open communications to the 
front. 

To improvise means of crossing 
obstacles. 

14. During the forward movement 

after deployment, it is neces¬ 
sary : 

To destroy or open passages 
through obstacles. 

To improvise means of crossing 
obstacles. 

To improve the cover against 
view and against fire. 

To construct obstacles. 

15. During the combat it is necessary, 

rush by rush, and step by step: 
To utilize the cover afforded by 
the ground. 

To improve this cover. 

To construct cover, where natu¬ 
ral cover is lacking. 

In general the principle is that when 
the skirmish line can no longer advance, 
it must dig in; one man out of two digs, 
while the other fires. 

16. During the assault, the assaulting 

troops: 

Will utilize the defiladed or cov¬ 
ered lines of approach. 

Will clear the routes to be fol¬ 
lowed. 

Will open passages through ob¬ 
stacles. 

Will improvise means of crossing 
obstacles. 

17. During the pursuit .—Troops fol¬ 
lowing the assaulting line will thor¬ 
oughly organize the ground won. 

18. In case of breaking off the fight. 
—The retirement will be effected under 
the protection of a position organized 
in rear by fresh troops utilizing the 
cover previously occupied and held. 


Use on the Defensive. 

19. The defensive organization of a 
natural supporting point and of a cen¬ 
ter of resistance are to be treated in 
later chapters, so that only the steps to 
be taken in case of emergency will be 
mentioned here. 

20. Improving the field of fire: 

Works permitting front and flank 

fire. 

Clearing the field of fire. 

Obtaining the ranges of various 
points in the field of fire. 

21. Construction of cover against 

sight and fire. 

22. Establishment of communica¬ 

tions: 

Forward to advanced positions 
for observation. 

Laterally, to connect the parts of 
the firing line. 

To the rear, to permit the rein¬ 
forcement of the firing line. 

23. Accessory defenses: 

Obstacles in front of the firing 

line. 

Measures to protect points of 
passage. 

Strengthening of intrenchments, 
building of shelters, com¬ 
manders’ stations, etc. 

PART IV. 

THICKNESS FOR DEFENSIVE AGAINST 

FIRE OF INFANTRY, ARTIEEERY AND 

trench weapons. 

24. The object of an intrenchment is 
to protect the defender, whether at rest 
or in the firing line, from hostile pro¬ 
jectiles. Its profile therefore depends 
upon the armament in use, and it is 
necessary to study the effect of projec¬ 
tiles.' » 



10 


Field Fortification 


Infantry Fire. 

25. The rifle, the machine gun and 
the automatic rifle, adopted by the dif¬ 
ferent powers, throw a cylindro-ogival 
bullet, which has at the short and mid¬ 
ranges a considerable remaining veloc¬ 
ity. Its penetration varies according to 
the ballistic force of the arm, the sub¬ 
stance traversed, and the form of the 
bullet. 

26. Bullet D ( French ) and Bullet S 
(German). —Bullet D is entirely of 
brass, of bi-ogival form, and 1.53 inches 
long, figure 1. Bullet S is formed by a 
core of lead, “ a,” figure 2, surrounded 
by a jacket of steel, “ b,” and plated 
with German silver. Its front part is 
cylindro-ogival; its rear part, cylindri¬ 
cal. It is 1.1 inches long. Bullet D 
weighs 197.5 grains and has an initial 
velocity of 2360 feet. Bullet S weighs 
154 grains and has an initial velocity of 
2820 feet. From 0 to 900 yards the 
trajectory of the bullet S is flatter than 
that of D; beyond 900 yards, the reverse 
is true. The accuracy of the bullet D 
becomes clearly superior to that of S, 
but the curved trajectory of the bullet S 
permits it to search depressions and to 
reach the reserves in rear. 

27. Thickness for protection against 
the German Bullet S (at all distances). 


Steel Shields. 

Sheet-steel.—2 sheets of steel of .16 
in., one behind the other at 1.2 in., prac¬ 
tically stop the bullet, as a third sheet is 
only dented. 


0.53") 

h-- 



Fig. \. _ 

Artillery shields of .2 in. are only per¬ 
forated at distances less than 350 yards. 
Shields for attack, and Parapet 



** - 

shields of special steel are not per¬ 
forated by the bullet S at distances 
greater than 150 yards. Two shields 


Nature of material 

Thickness 

Nature of material 

Thickness 

Earth (necessary thickness for all 
cases). 

3 ft. 4 in. 

Walls of rammed earth 

2 ft. 

Sand... 

2 ft. 6 in. 

Walls of brick. 

1 ft. 8 in. 

Manure . 

9 ft. 10 in. 

Walls of rubble. 

1 ft. 4 in. 

Saplings and soft wood. 

2 ft. 

Loose snow. 

9 ft. 10 in. 

Oak and hard wood. 

1ft. 4 in. 

Packed snow. 

3 ft. 4 in. 

3 ft. 4 in. 

Hay rick. 

19 ft. 8 in. 

Frozen snow 




Sand-bags.—Beyond 400 yards, one placed at a few inches from each other 
length of bag; from 400 to 100 yards, stop the bullet at 25 yards. Shields are 
\y 2 length; from 100 to 50 yards, 2 now being manufactured which stop the 
lengths; at less than 50 yards, 4 lengths, bullet at 50 yards. 





























F i e 1 d Fortification 


11 


Sheet-steel and Sand.—2 sheets of .12 
in. separated by 1.6 in. of sand stop 
the bullet at 10 yards. 

Wood and Sand.—The same result is 
obtained with a cover of 1.8 in. of oak 
and 2.4 in. of pine. 

28. Armor piercing bullets. —The 
Germans have employed a special 
armor-piercing bullet called SMK, of 
steel with a brass jacket and slightly 
truncated. This bullet perforates the 
special steel sheet of less than .47 in. at 
all distances, and of .55 in. at 50 yards. 
The resistance of the plate increases 
rapidly with the angle of incidence of 
the bullet. 

The bullet S turned end for end in 
the shell has a great penetrative power 
at short range, but it then acts like a 
dum-dum bullet. 

By truncating the bullet D so that it 
presents a cross section at .1 in. from 
the point, a great penetrative power 
against shields is given for short ranges 
(Fig. 3). A steel bullet has recently 
been put into the French service. 



fi<j. 3-- 

Artillery Fire. 

29.— Employment. —In field warfare 
the French Artillery uses projectiles 
with wide range of action; it employs, 
for this purpose, high explosive shell 
and shrapnel. The high explosive shell 
of the 75 (2.9 in.) fired with sufficient 
density, due to its rapidity of fire, has 
a terrible effect on dense formations. 
Most of the guns used have a flat 
trajectory. 


The German Artillery, on the con¬ 
trary, has preferred heavy projectiles, 
fired with large angles of fall, with vio¬ 
lent but very local action; so, in spite 
of a prodigious expenditure of these 
projectiles, the results have been small. 

In position warfare, the 75 (2.95 in.) 
gun has always played a preponderant 
role, while the German 77 (3.03 in.) has 
not been nearly so effective. Moreover, 
if the heavy artillery is compared, the 
long French projectiles are superior to 
the German of the same calibre by 
reason of the greater weight of ex¬ 
plosive that they carry. 

30. Action of the projectiles. —Shells 
bursting at a certain distance above the 
ground, either before reaching it (fuse) 
or after ricochet, produce two kinds of 
sheafs, viz., narrow and open. Shells 
bursting upon impact or after slight 
penetration (delayed action) are used 
either against personnel or for the de¬ 
struction of obstacles. In general, the 
same projectile can be used for either 
purpose. 

31. Shell used against personnel .— 
For this purpose there are used shrap¬ 
nel of 77 mms. (3.03 in.), 90 mms. 
(3.5 in.), 10 cms. (3.93 in.), 13 cms. 
(5.12 in.), 15 cms. (5.9 in.), and 21 
cms. (8.27 in.) which contains 170 lead 
balls of 26 grammes and 135 steel 
balls of 150 grammes. These balls are 
more than 1.2 in. in diameter and can 
act efficiently against shields. 



F.g.*.- 

The combination shell 105 (4.13 in. 
light howitzer) is also used for this 
purpose. It is fired like shrapnel, time 
or percussion. 

32. Shell with closed sheaf. —In the 
shell bursting at E (Fig. 4), the balls 





Field Fortification 


12 


which it contains are thrown into the 
interior of a cone having for an axis 
the tangent ET to the trajectory. 

The trace on the ground is oval in 
form, the part with most hits (effective 
zone) being situated nearest the burst¬ 
ing point (Fig. 5). 



«- 1*/Q -H-- 1 

Fig. 5. - ( 272 yds) 

For a given ball, the danger zone then 
comprises all the distance AC on the 
ground on which a man standing will be 
hit (Fig. 6). The flatter the trajectory 
the longer will be AC. 


V//W777. 




Fig. 6. — 

If the personnel is sheltered behind a 
parapet, the flatter the trajectory and 
the narrower the sheaf the more the 
personnel will be sheltered. The more 



If the personnel is protected by a 
roof covered with 4 in. of earth, the 
balls will be stopped. 

When the shells are percusson fired 
for a small angle of fall (15°, Fig. 8), 



//SwJW) '> /// s/s/S/7~ 


they burst after the ricochet; the sheaf 
obtained sweeps the ground well as long 
as the angle of rise remains small; this 
angle increases with the angle of fall; 
a time may come when all the sheaf will 
pass over the target. 

23. Shell with open sheaf .—The 
necessity for reaching the personnel be¬ 
hind a parapet or behind vertical shields 
has led to the invention of projectiles 
giving a sheaf of balls or fragments 
spreading in a direction approaching the 
normal to the trajectory. To this type 
belong the French “ unit ” shell, and the 
German high explosive shell of the 77 
gun and 105 howitzer. The German 77 
high explosive shell bursting with time 
fuse, gives a hollow sheaf of 114° (Fig. 
9). This sheaf is composed of fairly 



|] 


Hcf. 7. 

curved the trajectory and the more 
open the sheaf the more the personnel 
will be exposed (Fig. 7). 


TV > ? ? s / yj/v /y /> s V ; / 

Fig. 9- — 

large fragments, few in number, and 
of low initial velocity. Certain frag¬ 
ments are still effective at 15 yards, as 
a maximum to right and left. The 
action is very local, and none at all if the 
fire is not well regulated, on account of 
the narrowness of the sheaf. 














Field Fortification 


13 


The German shell of the light how¬ 
itzer has very thick walls, and small ex¬ 
plosive chamber. The sheaf is hollow, 
more open than the preceding one 
(200°, Fig. 10). The radius of action 



Fig. 10.- 

is 25 yards. There is the same diffi¬ 
culty of regulating fire as for the pre¬ 
ceding type. 

34. Shells used against materiel: 

Shrapnel, old type and modern .— 
These projectiles have sufficient power 
to be employed with percussion fuses 
against the materiel of artillery, walls, 
houses, etc. 

High explosive shell .—As the use of 
the delayed action fuse may impair the 
action of the high explosive shell in 
certain cases, instantaneous detonating 
fuses are used. Shells provided with 
these burst immediately upon impact. 
They are used advantageously against 
walls, materiel, parapets, barbed wire 
entanglements, abatis, etc. Fired into 
the earth, these projectiles produce 
craters. They can therefore destroy 
heavy parapets. Against masonry cov¬ 
ered with earth, delayed action fuses 
are used. 

The German 90 mm. shell (3.54 
in. with .36 lbs. of explosive) and 
that of the 77 mm. (3.03 in. with the 
same explosive charge) give results 
very inferior to those of the French 
75 mm. 

The German 105 mm. shell (4.13 in. 


with 2.2 lbs of explosive) is more ef¬ 
fective than thatof the 11 mm. 

The German shell of the heavy how¬ 
itzer, 15 cms. (5.9 in. with 10.36 lbs. of 
explosive) is intended to act by its 
fragments. These can penetrate artil¬ 
lery shields at 40 yards to the right 
and left, 5 yards forward and 25 yards 
to the rear. 

The German 10 cm. shell (3.93 in. 
with 4.4 lbs. of explosive), that of 13 
cm. (5.12 in. with 8.8 lbs.) and that of 
the 15 cm. (5.9 in.) gun give results 
similar to those of the heavy howitzer. 

The German 21 cm. shell (8.27 in. 
with 33 lbs. of explosive) is intended 
to be used against steel plates and con¬ 
crete ; it is often used against buildings. 
Its effect is very destructive but local. 

The German 28 cm. shell (11.02 in. 
with 22 lbs. of explosive), armor pierc¬ 
ing, or semi-piercing, with very strong 
ogive, is intended for concrete and 
masonry. It gives craters of small 
dimensions. 

The German 305 mm. shell (12 in. 
with 44 lbs. of explosive) or Skoda 
mortar, armor-piercing projectile, is 
intended to attack concrete forts. 

The German 42 cm. shell (16.5 in. 
with 88 lbs. of explosive) is employed 
for a similar purpose. In a mass of 
concrete it produces a wide but shal¬ 
low crater, and can produce serious 
trouble in the delicate machinery of 
forts, such as turrets, etc. 

Fire of Trench Weapons. 

35. To the fire of Infantry and Artil¬ 
lery is now added that of Trench 
Weapons. These weapons, such as 
bombs, grenades and torpedoes, can be 
compared, so far as their effect is con¬ 
cerned, to the artillery projectiles. In 
France, bombs and grenades, thrown by 
hand or by machines of low power 





14 


Field Fortification 


(cross-bows,' slings, howitzers, mor¬ 
tars) give, on bursting, fragments which 
are similar to those of the 75 mm. shell. 

Their force ceases to be deadly be¬ 
yond 25 yards. Bombs and torpedoes 
thrown from 500 to 1800 yards by ap¬ 
paratus of high power (guns of 58,240 
and 340 mm. (2.28, 9.48 and 13.38 in.) 
and howitzers of 75 mm.) and contain¬ 
ing from 35 to 220 lbs. of explosive, 
produce craters as deep as those caused 
by projectiles of the heaviest calibres. 
They cause the destruction of shelters, 
protected by armor and concrete, as well 
as the cave shelters more than 26 feet 
underground. 

36. The Germans employ bombs, 
grenades and torpedoes similar to the 
French. Their bombs and torpedoes 
are thrown by Minenwerfer of different 
models. The principal ones are: 

Of small calibre, 7.5 cm. (2.95 in.) 
weighing 108 lbs., range 1150 yards, 
projectile weighs 10.1 lbs. and contains 
2.2 lbs. of explosive. It is called a 
light mine. 

Of medium calibre, 17 cm. (6.7 in.), 
range 850 yds., projectile contains 15.4 
lbs. of explosive; called a medium mine. 

Of heavy calibre, 24.5 cm. (9.64 in.) 
weighing 1322 lbs., range from 450 to 
900 yds., projectile weighs 220 lbs. and 
contains 110 lbs. of explosive; called a 
heavy mine. 

37. Thickness for protection against 
light artillery and trench weapons of 


38. Thickness for protection against 
heavy artillery and trench weapons of 
high power: 

150 mm. (9.5 in.) howitzer: 2 layers 
of saplings of 6 in. and 2 layers of 
earth of 1 ft. alternated. 

210 mm. (8.26 in.) howitzer: 3 lay¬ 
ers of saplings of 6 in. and 3 layers of 
earth of 1 ft. alternated and reinforced 
by flagstones, sacks of cement, rubble, 
or railroad rails. 

280 mm. (11.02 in.) howitzer and 
calibres above: 17 to 33 feet of undis¬ 
turbed earth (cave shelter). 

39. Blast. —Besides the metal frag¬ 
ments, there is the blast against which 
protection must be provided. This 
blast is caused by the explosion of the 
projectile, and is strong enough to over¬ 
turn walls, break in doors and knock 
furniture and men about. The commo¬ 
tion produced results in nervous effects 
often mortal. Moreover, the action of 
the gas produced is very dangerous and 
causes long and serious illness. Their 
effects are not usually noticed for some 
days after the explosion, and they pro¬ 
duce loss of hearing, sense of smell, of 
taste, of sight, as well as paralysis, and 
prolonged fainting spells. The cure is 
very slow. 

Protection against this double effect 
of blast is obtained by: 

1st. Making the trenches as narrow 
as possible. 


low power: 2d. Dividing up the works into small 

Fuse 

Nature of material 

Direct hit 

Oblique hit 

Time ,.,. 

Low earth. 

16 ill. 

4 in. 

3 in. 

6 in. 

Percussion. 

Hard wood. 

6 in. 

Soft wood. 

10 in. 

Brick. 

2 Yz in. 

.1 in. 

3 ft. 4 in. of earth. 

7 to 10 ft. of earth. 

Steel sheet. 

Projectiles of the 77 mm. gun. 

Projectiles of the 105 mm. howitzer.. 























Field Fortification 


15 


sections by increasing the number of 
traverses. 

PART V. 

INTRENCHING TOOLS FOR INFANTRY, 

CAVALRY AND ENGINEERS. 

40. Two things are needed for field 
works: men and tools. The men are 
supposed to be engineer soldiers; as a 
matter of fact, they are almost always 
infantry men. 

Troops of all arms have a supply of 
tools which comprises: 

Tools for earth work—shovels, picks 
and pick mattocks. 

Tools for demolition — hand-axes, 
bolos, wire cutters, axes, crowbars, and 
saws. 

Tools are classed as portable tools, 
carried on the person of the soldier; 
and park tools, carried on wagons or 
pack mules. 

41. Tools for Infantry: 

Portable tools for each company: 

34 pick mattocks, with carriers. 

17 wire cutters, with carriers. 

8 hand-axes, with carriers. 

9 bolos, with scabbards. 

68 shovels, with carriers. 

Park tools for each regiment: 

26 axes. 

7 crowbars. 

150 pick mattocks. 

450 sand bags. 

13 saws, hand. 

13 saws, two-man. 

300 shovels. 

42. Tools for Cavalry: 

Portable tools for each troop: 

8 hatchets with covers. 

24 picks, with covers. 

72 shovels. 

105 wire cutters. 

1 sledge hammer. 

Park tools for each regiment: 

26 axes. 

7 crowbars. 


150 pick mattocks. 

13 saws, hand. 

13 saws, two-man. 

300 shovels. 

450 sand bags. 

In addition each squadron has a 
demolition outfit carried on a pack mule. 

43. Tools for Engineers: 

Each company carries in 2 tool 

wagons: 

4 adzes. 

26 axes. 

2 pinch bars. 

4 sledge hammers. 

6 hatchets. 

18 gabion knives. 

36 machetes. 

4 mauls. 

4 peevies. 

6 picks, railroad. 

36 pick mattocks. 

18 pliers. 

2 posthole diggers. 

2 saws, 1-man. 

4 saws, 2-man. 

72 shovels. 

Miscellaneous tools and sup¬ 
plies, including demolition 
and carpenter tools. 

In addition 8 pack mules carry mis¬ 
cellaneous tools and supplies for in¬ 
trenching, pioneer and demolition work. 

Each battalion headquarters carries 
in a wagon a complete blacksmith’s 
equipment. 

For complete lists of above equip¬ 
ments see Unit Accountability Manual 
issued by A. G. O. 

44. The duties of the Engineer troops 
in connection with field fortification 
pertain both to the attack and the de¬ 
fense and include the selection of defen¬ 
sive positions when out of the presence 
of the enemy; rectification of and as¬ 
sistance in the- selection of such posi¬ 
tions in the presence of the enemy; the 





16 


Field Fortification 


location, design, and construction of the 
more important field works; assistance 
in and supervision of the construction 
of the hasty defenses wherever pos¬ 
sible ; the supply of tools and materials, 
and the reconnaissance, demolitions, 
water supply and communications inci¬ 
dent thereto. 

conclusion. 

45. Such is the matter preliminary 
to a study of field fortification. This 
subject must be thoroughly studied for 
proper preparation for modern war¬ 
fare. The time has passed for “ram¬ 
parts of human breasts,” and the war¬ 


like ardor which will break up all 
assaults.” We must know how to 
dig and how to make war with pick and 
shovel as much as with weapons. Ex¬ 
perience has shown us that courage 
must be sheltered until it can be usefully 
employed in the open. 

It is the daily work, faithfully done 
in all weathers and under all circum¬ 
stances, that gives glorious results. 
There is no undignified element in war¬ 
fare. The men who dig and work at 
transport of supplies and ammunition 
are as meritorious as those who fire and 
charge. They all work to a common 
end—for the common defense. 



CHAPTER II 


UTILIZING NATURAL COVER, PROFILES AND EXECUTION 
OF LIGHT FIELD FORTIFICATIONS 


PART I 

INFANTRY. 

1. Its mobility: 

The infantryman marches slowly but 
is capable of prolonging his advance 
either by day or night, in hot or cold 
weather, on all terrain, far or near the 
enemy and in spite of the latter’s fire. 
This characteristic enables infantry to 
approach an enemy, attack him with the 
bayonet, and drive him from the posi¬ 
tions he occupies. 

2. Ability to utilize natural cover: 

Infantry, more than any other arm, 

is capable of utilizing the shelter and 
cover of the terrain. The terrain is its 
natural ally. This ability to utilize the 
terrain enables it to economize strength 
and reduce losses. 

To enable him to advance under fire 
the infantryman has been supplied with 
fire arms. To increase his ability to 
utilize the terrain, he has been supplied 
with tools which enable him to make 
temporary shelters and to organize 
strongly the positions won. 

The infantryman thus acquires, by a 
combination of arms and tools, the abil¬ 
ity to take and hold the terrain he has 
won from the army. As the Russian 
Captain Soloview remarks: 

The infantryman should regard his 
spade as the faithful friend of his rifle 
and not consider it a useless load. 


PART II 

CONCEALMENT AND PROTECTION. 

3. A screen or mask consists of 
hedges, crops, underbrush, etc. which 
hide the rifleman without, however, pro¬ 
tecting him from fire. 

4. Cover or shelter consists of walls, 
earthworks, etc. which protect the rifle¬ 
man from fire. 

5. On the battlefield, natural features 
that screen and shelter should be util¬ 
ized as much as possible, as they pos¬ 
sess the following advantages over arti¬ 
ficial works: 

(a) Their organization demands less 
work. 

( h ) Concealment is easier. 

(c) From their nature, it is difficult 
for the enemy to estimate, for a given 
length, the number of men sheltered. 

6. They possess, however, certain dis¬ 
advantages : 

(a) The protection is sometimes so 
excellent that, morally as well as mate¬ 
rially, it becomes difficult to leave the 
shelter. 

Example: quarries with obstructed 
exits. Therefore, good judgment must 
be exercised in the selection. 

(b) Some of them are too visible. 
Example: large hedges. In this case 
their range can be easily found. 

As a general rule, do not occupy them 
uniformly and do not change the ap¬ 
pearance of the organized parts. 

7. Organization of the cover: 


17 


18 


Field Fortification 


To organize the cover which pro¬ 
tects troops from fire, construct suitable 
positions for firing and resting. To 
utilize the screens which merely hide 
the troops without protecting them 
from fire, dig trenches behind these 
screens in the following manner: 

(a) Choose the points which give the 
best field of fire. 

( b ) Construct cover for firing. 

(c) Construct a shelter. 

The constructions are usually “ indi¬ 
vidual ” in the first period of work; af¬ 
terwards, they are organized “ collec¬ 
tively.” The covers are: (1) for 
riflemen lying down, ( 2 ) for riflemen 
sitting down, and (3) for riflemen 
standing up. 

INDIVIDUAL ORGANIZATION OF NATURAL 
COVER 

8. Examples of hasty individual 
cover behind trees, bushes, or branches: 

(a) Fallen tree (logs or branches), 
the height of which is at a maximum of 
1 foot above the ground: 



Fig. 1. —Use of the cover without improve¬ 
ment. 



Fig. 2 .—First Period. 



- o,8o — --*< 

( 7‘11 


Fig. 3. —Second Period. 
Progressive improvement of the cover. 


( b ) Fallen tree, the top of which is 
more than 1 foot above the ground. 



Fig. 5. —Second Period. 



Fig. 6 .—Third Period. 


Wood which does not afford sufficient 
protection against bullets must be rein¬ 
forced by earth at the right and against 
the cover 1 foot behind. The three 
figures above show the progressive im¬ 
provement of the cover. 



Fig. 7. —Sharp ridges, furrows, or top of a 
crest at the end of a gentle slope. 


9. Examples of hasty individual cov¬ 
ers behind a furrow, a crest, a heap of 
sand or earth: 

Dig the ground as near as possible to 
crest A of the furrow in the manner in¬ 
dicated for the cover installed behind 
a fallen tree more than 1 foot high. 



Fig. 8 .—Narrow furrows. 


Use the earth excavated between fur¬ 
rows A and B to build up the earth be- 














Field Fortification 


19 


tween furrows B and C and fill up fur¬ 
row C; continue afterwards as for the 
sharp ridge. 



Fig. 9.—Low wall of earth, or earth and 
sand heaps, more than 2 feet high (two 
methods, A or B). 


(A) Lower the height about 8 inches ; 
throw the earth forward. Dig a trench 
as indicated in the figure. 

(B) Make a loophole in the pile of 
earth, showing oneself as little as possi¬ 
ble. Improve the firing position by 
making a place for the right leg and an 
elbow rest. 

10. Examples of hasty shelters (indi¬ 
vidual) arranged behind a large stone 
or heap of stones: 

A heap of stones, the top of which is 
1 foot at a maximum above the ground : 



Fig. 10.—First Period. 



GENERAL ORGANIZATION OF NATURAL 
COVER 

11. This consists in connecting up 
and co-ordinating the individual work 
under the direction of the squad com¬ 
mander. The work should be carried 
out on the lines adopted for the indi¬ 
vidual work; and the rules prescribed 
for the construction of artificial cover 
(profiles, depths, various shelters) 
should be followed as far as possible. 
In arranging the cover, the squads 
should utilize the natural features of 
the terrain. 



Fig. 12 .—Arrangement for a mound of earth. 



Fig. 13.—Arrangement for a dry ditch. 


t* r> 

+ o,Go 



r 


Fig. 14.—Arrangement for a sunken road 
defended on the side towards the enemy. 



Fig. 15.—Arrangement for a sunken road 
defended from the rear. 


12. Ditches full of water, drains, 
streams: 

























20 


Field Fortification 



Fig. 16.—Arrangement of a large ditch. 



Fig. 17.—Arrangement of a ditch full of 
water. 


13. Ordinary roads, road and rail¬ 
road embankments, and sunken roads: 



Fig. 18.—Arrangement of an ordinary road 
defended on the side toward the enemy. 



Fig. 19.— Same defended from the rear. 



Fig. 20.— Road embankment, defended from 
the rear. 



Fig. 21. —Arrangement of a railroad 
embankment. 



Fig. 22.—Arrangement of a sunken road. 


14. Hedges and woods: 

Dig a trench behind the hedge and 
throw the earth against it; make open¬ 
ings in the hedge to facilitate view and 
fire (Fig. 23). If the hedge is low 
deepen the trench, but make the para¬ 
pet lower than the hedge which 
masks it. 




Fig. 24.— Arrangement of the edge of a wood. 


Avoid destroying the natural appear¬ 
ance of the wood; do not cut the trees 
and brush on a certain depth, but cut off 
branches where necessary to obtain a 
field of fire. Behind this strip cut the 
brush and small trees so as to make a 
path 3 to 4 yards wide. Construct a 
trench behind the mask of trees. The 

























Field Fortification 


21 


parapet can be raised up to 2 or even 3 
feet. Construct abatis on the parts of 
the border of the wood, where it will 
not interfere with the fire. 

15. Walls: 

(+167+0,80 -r—_..- x 


Fig. 25.—Arrangement of a wall, 2~feet 
8 inches high. 



Fig. 26.—Arrangement of a wall 8 feet high. 



Fig. 27.—Arrangement of a wall more than 
8 feet high without making loopholes. 



Fig. 28.—Arrangement of an iron fence built 
on a low wall. 

PART III 

ORGANIZATION OF ARTIFICIAL, IN- 
TRENCHMENTS. TYPES of eight 
FIELD FORTIFICATIONS. 

16. An intrenchment is a “ cover ” 
arranged so as to permit firing. It is 
natural if it is arranged by using any 


existing cover, such as: walls, ditches, 
earth heaps, etc. It is artificial if it is 
entirely constructed. In any case it 
must provide: 

A cover against hostile fire. 

An obstacle to the movements of the 
enemy. 

View to enable the occupant to fire 
and obtain information of the enemy. 

Communications for the rapid trans¬ 
mission of orders and supplies. 

17. Conditions which a field fortifica¬ 
tion should fulfil : 

(a) A clear field of fire: This is the 
primary condition to which all others 
must be sacrificed. This condition re¬ 
quires considerable height for the para¬ 
pet. But in order to avoid visibility and 
to interfere with the hostile artillery 
range-finding, a low parapet is advan¬ 
tageous. Considerable height can be 
used, but only when the skirmish line 
is burrowing into the ground and the 
tactical necessities prevent the careful 
siting of the work. In this case it may 
be indispensable to raise the parapet to 
a height which will establish the work 
entirely above the level of the ground. 

2. Protection from fire: 

In the old intrenchments, protection 
was obtained by the thickness of the 
parapet. Protection is now obtained in 
the intrenchment with a low parapet, by 
entirely concealing the riflemen in a 
narrow and deep trench. Protection 
from oblique and enfilade fire and blast 
is obtained by the use of traverses. 

Protection against grenades i$ ob¬ 
tained by proper slopes of the parapet 
and parados ; and by an arrangement of 
wire netting which stop these projectiles 
and throw them back. 

To complete the protective arrange¬ 
ments, shelters can be constructed of 
earth and timber, which will give pro- 


























Field Fortification 


c 2 c 2 


tection from the 105 mm. (4.1 in.) and 
150 mm. (5.9 in.) shells. 

3. Positions suitable for firing and 
resting: 

Proper and suitable positions are in¬ 
dispensable. Troops suffer from cramp 
by a prolonged stay in trenches too 
narrow and unsuitable, and they cannot 
advance or retreat. The best arrange¬ 
ment is to provide a bench about 5 feet 
below the interior crest on half of the 
trench; it affords a step from which to 
fire standing, and a seat. In order to 
fire accurately, the rifleman must have 
an elbow rest; in order to be steady 
when firing, he must have a loophole; 
to fire at night with the maximum of 
accuracy, it is necessary to establish 
fixed firing points. Finally, the dimen¬ 
sions must correspond to the average 
height of a man. 


18. Types and profiles of regulation 
trenches for light field fortification: 

A profile is a section of any cover 
made by a vertical plane perpendicular 
to its axis, or practically parallel to the 
direction of fire against and over it. 

Although officers are authorized to 
modify the regulation types, the infan¬ 
tryman should be taught to execute au¬ 
tomatically a single type. Experience 
has shown, moreover, that it is neces¬ 
sary to establish fundamental dimen¬ 
sions which are the best; they must be 
thoroughly known, and carried out on 
the ground to within 2 inches by the 
N. C. O.’s who should be supplied with 
measuring rods. 

19. Execution of the skirmisher’s 
trench by a skirmish line: 



Fig. 29. —First Period. The 
soldier AB digs in F and 
makes a cover between the 
2 sacks, S and S'. 



Fig. 30. —Second Period. 
The soldier AB is ready to 
fire in F; the soldier CD digs 
in F' and makes a cover to 
the right of his pack to pro¬ 
long the preceding cover. 



B| D| 


Fig. ,51.—Third Period. The 
soldier AB starts working 
again, between F and F', and 
thickens the cover; the 
soldier CD is ready to fire in 
F '; he draws his pack over to 
his side. 


4. A profile that is progressive and 
rapidly executed; affording cover and 
permitting firing while it is being con¬ 
structed : 

From the skirmisher’s trench to the 
complete trench, with a rest bench and 
even revetment, the profiles of the 
trenches must be obtained successively, 
rapidly and without any change in the 
work already accomplished. 



Fig. 32. —Section through F (Second 
Period). Fourth Period and the Following: The 
two soldiers, AB and CD, work and fire 
alternately; they straighten up as they dig 
down. The packs are taken down as soon as 
possible, as they are very conspicuous. 








Field Fortification 


93 


20. Sitting trench: 



Fig. 33.—Sitting Trench. This is the 
first result of the work executed methodi¬ 
cally and by a group. It is the profile which 
the firing line under the necessity of stop¬ 
ping and taking cover should endeavor to 
accomplish. The relief of the parapet above 
the firing banquette is 2 feet; above the 
bottom of the trench, 3 feet 4 inches. Time 
for construction: 30 minutes to one hour. 

21. Kneeling trench: 

(+ n 
+©,4o 



Fig. 34.—Kneeling Trench. This profile 
is obtained by excavating the banquette. 
Protection is greater (Fig. 24). Relief: 3 feet 
4 inches. Time for construction: 10 to 30 
minutes from the sitting profile; or 30 minutes 
to 1)4 hours from breaking ground. 

22. Standing trench: 

(•♦1')+o,3o ♦ o,3©(*t) 



Fig. 35. —Standing Trench. This is used 
when it is necessary to be firmly intrenched 
or when a halt is made of sufficient duration 
to permit its construction. To execute it, the 
kneeling trench is increased 1 foot 8 inches 
in depth. Thus a depth of 4 feet is obtained, 
which affords a better shelter than the trench 
3 feet 8 inches in depth; and it is easier to 
raise the banquette than to repair the damage 
resulting from its being lowered. 


23. Complete trench: 

This profile fulfils all the conditions 
for a field trench (shelter, convenience, 
rest). 


+o,3oM') 



Fig. 36.—Complete Trench. When the 
trench is finished, it will have a width of 
3 feet 4 inches at the top, and 2 feet 8 inches 
at the bottom. A parados should be provided 
as a protection from shell splinters. The base 
of the parados should be one foot from the 
edge of the trench. Relief: 5 feet above the 
firing banquette; 6 feet 4 inches above the 
bottom of the trench. Time for construction: 
45 minutes to 2 hours from the standing 
trench; or 1)4 to 2)4 hours from breaking 
ground. It varies largely, depending upon 
how tired the men are, material and tactical 
circumstances under which they operate and 
on the tools at their disposal. 

24. Profiles on difficult ground: 

(a) Rocky ground or in woods : 

To lessen the work in stony ground or 
when the trench is masked by woods, 
the depth is diminished and the height 
of the parapet increased. 


-»-o,«©(+2) 



Fig. 37. —Profile on rocky ground or in 
woods, or increased command required by 
tactical conditions. This is also the profile 
to be adopted when the skirmish line hugs 
the ground and the tactical necessities pre¬ 
vent the careful siting of the work. (See 
Par. 17-1.) 




















24 


Field Fortification 


( b ) Damp ground: 

In order to maintain the trench walls 
it is necessary to thoroughly revet them 
with hurdles, expanded metal, wood, 
sand bags, etc. At the bottom, a board 
or grating should be placed; and the 
firing banquette should be made of fas¬ 
cines held together with pegs. 



( c ) Very wet ground: 

When the water is very close to the 
surface, 1 to 2 feet, it is impossible to 
excavate on account of constant flood¬ 
ing of the trenches. Two ditches should 
be dug, one in front and one behind the 
line of resistance, to receive the water. 
The parapet is constructed by using 
gabions, fascines, sand bags, etc. 



Fig. 39.—Profile on very wet ground. 


( d ) In woods on a hillside: 

A layer of logs covered with earth 
forms the parapet. Drainage is secured 
with a grating in the bottom of the 
trench, and drains every ten yards. 

25. Shelter for machine guns: 

A two-gun emplacement is shown in 
Fig. 41. The guns are emplaced at an 
interval of 10 to 15 yards; arranged so 


that they shall not both be disabled by 
shell fragments from the same projec¬ 
tile ; and to permit repairs, and the pro¬ 
tection of the gun crews. The con¬ 
struction is progressive, so that the guns 
are always ready to fire. The platform 
is semicircular, with a parapet, first for 



Fig. 40.—Profile in woods on a hillside. 


firing lying down, with a parapet one 
foot high; afterwards for normal firing, 
with a parapet one foot high and an ex¬ 
cavation 1 ft. 8 in. deep for the gun. 
A ditch, dug progressively, shelters the 
gun crews; it is first dug to a depth of 1 
ft. 4 in. for firing kneeling; then to a 
depth of 2 ft. 8 in. for firing in a normal 
position. 


Section A 3 









































Field Fortification 


25 


26. Individual disposition: 

(a) Each rifleman arranges the bot¬ 
tom of the trench or the firing banquette 
(lowering or raising it) to suit his 
height. 

( b ) He makes a notched loophole in 
the crest of his parapet. 

( c ) He constructs an arrangement 
for firing at night; this is verified by 
the squad or section leader. 

( d ) He makes a recess in the front 
wall of the trench for ammunition. 

( e ) Concealed shelters are at once 
constructed for the men on watch, their 
heads are concealed by bunches of grass, 
branches, etc. 

27. Collective dispositions: 

(a) Concealment of the trenches: 

They should be made as invisible as 

possible, and their concealment should 
be completed by treating the front 
slope of the parapet so that its appear¬ 
ance will correspond to that of the sur¬ 
rounding* ground. Crops should be re¬ 
placed, where disturbed, and carefully 
arranged; bushes should be planted to 
hide the parapet, the men on watch, the 
riflemen, and the commanders. Sod 
should be preserved and placed on the 
parapet and parados. 

( b ) Construction of dummy trenches: 

Dummy trenches and works should 

be freely employed so as to deceive 
the enemy as to the strength of the de¬ 
fender and to scatter his fire. These 
works should be made slightly more 
visible than the regular works, so as to 
attract the attention of the enemy, with¬ 
out causing him to suspect their true 
nature. It is also necessary to simulate 
their occupation; and the damage 
caused to them by artillery fire must be 
repaired, so that the enemy will not 
discover his mistake. 

(c) Drainage: 

One of the most important arrange¬ 


ments in the construction of trenches is 
that for drainage. Besides the accidents 
and diseases that are likely to occur dur- 



Fig. 42.—A “Bait-trench” can be em¬ 
ployed. Two trenches, AB and CD, are con¬ 
structed between two works, X and Y, about 
60 yards apart. These trenches should be 
under enfilading fire. A sap starting from 
BC serves as a bait. 

ing a prolonged stay in water, it often 
happens, that if the drainage is 
neglected, it will be impossible to occupy 
the trench during wet weather. To 



Fig. 43. 

drain the water from the bottom of the 
trench, it is necessary to slope the bot¬ 
tom towards the rear where a drain 
should be constructed to allow it to 



Fig. 44. 



run off (Fig. 43). If the bottom of the 
trench does not have a natural slope 
along its axis, a slope must be given to 
the drain. In damp ground, it is merely 
necessary to receive the water in buried 
























26 


Field Fortification 


barrels or pits, filled with filtering 
material (Fig. 44). The walls of these 
pits are maintained by sinking in one 
or more gabions. They are dug at 
the end of special short communication 
trenches; the entrance to these trenches 
should be barricaded. 

In less permeable ground, an en¬ 
deavor should be made to reach a per¬ 
meable layer by boring with an earth 



auger. The boring will be assisted by 
successive explosions of detonators, and 
an enlargement of the hole can be made 
at the desired depth with a small charge 
of explosive. In hilly ground, the water 
can be run off by ditches or even by 
pipes placed under the parapet. The 
ditches (Fig. 45) must be large, with 
sloping sides, to prevent their being ob¬ 



structed by the sides caving in. If a 
permeable layer cannot be reached, or 
if the volume of water is too great, 
the water is emptied from the pits 
with buckets, scoops, etc. Pumps are 
often used, and to insure their good 
working a strainer is necessary, and the 
bottom of the pit should be lined with 
bricks or tiles. 

The water should be run off promptly, 


otherwise the bottom of the trench be¬ 
comes muddy, and the muddy water 
soon renders the pumps useless. 

The best and only means of making 
the bottom of trenches practicable is to 
install a floor or grating (Figs. 46 and 
47) formed of two sills, 2 l / 2 to 3 inches 
in diameter supported on ties which rest 
on stakes sunk into the ground. On 
the sills, poles, 2 to 2 y 2 inches in diame¬ 
ter are nailed at intervals of an inch. 
Instead of poles, boards can be used, 
but they should be covered with wire 
netting, to prevent slipping. The floor 



should be made in sections, from 2 to 4 
feet in length and interchangeable. This 
work requires a great quantity of tim¬ 
ber or lumber, and makes their con¬ 
struction difficult in great lengths. 

If timber or lumber is not available, 
a central or two parallel ditches filled 
with broken stone can be used in the bot¬ 
tom of the trench, and usually provides 
good drainage. 

( d ) Revetment: 

The trench walls, the seats, benches 
and steps in soft ground, especially if 
they are likely to be much used, should 
be revetted. If possible this should be 
done when the trenches are first con¬ 
structed. 

When of planks or boards, they 
should be placed on top of each other, 
behind stakes, and backed up with earth 











Field Fortification 


27 


(Fig. 48). The stakes should be driven 
in at the foot of the slope at the desired 
inclination and at intervals of from one 
to two yards. Every second or third 
stake should be anchored to stakes under 
the parapet by means of wire withes 
or rope, fastened at about two-thirds of 
the height of the revetment. 

When of branches or brush, the 


+i, Ho ova") 



branches or brush is heaped up, like the 
boards, behind the stakes and suffi¬ 
ciently pressed together that the earth at 
the back does not filter through (Fig. 
49). If it is not desired nor possible 
to anchor the stakes separately, a pole 
can be fastened along them near the top, 
and this can be anchored at intervals of 
from 4 to 6 feet. 



When of woven brush, the pickets are 
driven at intervals of from 1 to feet: 
they are temporarily joined together at 
the top with a pole. The wattles are al¬ 
ternately passed in front and behind the 
pickets and interwoven. The pickets 
should be anchored. 

When of hurdles, these are especially 
suitable when used after a work is fin¬ 


ished to strengthen it. For method of 
construction see Engineer Field Man¬ 
ual, page 374. They are placed close 
together, and the sharpened stakes sunk 
into the ground and anchored (Fig. 50). 



Fig. 50. 


When of sod or brick, the sods should 
be cut to a size of 18 X 9 X 4*4 inches. 
They are laid grass down, like brick ma¬ 
sonry. If bricks are used the method of 
laying them is the same. 

When of fragments of hard earth, 
stones and sand bags, the method of con¬ 
struction is the same as for sod or brick. 

When of expended metal, this forms 
an excellent revetment. It should be 
supported by stakes about 2*4 inches in 
diameter, at intervals of 18 inches; the 
stakes should be anchored, and the 



metal fastened to them with staples 
(Fig. 51). 

When of fascines, their use is sug¬ 
gested for wide trenches, but they are 
usually used for making steps. 

When of gabions, they are used in 











28 


Field Fortification 


very wide trenches, such as assembly 
points. They are placed side by side. 
(e) Steps: 

Trenches must be provided with an 
arrangement that will permit troops to 
move forward out of the trenches. 
These steps should be revetted with 



one or more rows of fascines (Figs. 52 
and 53). 


Ladders have the advantage of not 
widening the trench. They are placed 



vertically against the wall of the trench 
(Fig. 54). 

Ramps parallel to the firing trench 
may be constructed at the ends of the 



branches of a zig-zag communicating 
trench. 

(/) Drinking water, a supply of 
drinking water for the trenches should 
be provided. 

(g) Materials, a supply of straw, 
planks, stakes, and brush serves for pro¬ 


tection in inclement weather; and en¬ 
ables the defenders, in the intervals be¬ 
tween fighting, to improve the interior 
organization, revetments, shelters, tra¬ 
verses, etc. 

PART IV 

trace; ot intre;nchme;nts. 

28. In the trace of intrenchments, the 
direction must be frequently changed 
to avoid enfilade fire. A rifleman shoots 
perpendicularly to the line of his cover, 
or at most at 30° to the right and left 
of this line. Placed at point P (Fig. 55) 



his fire will cover, at most, a sector 
whose angle will be 60°. The angle 
AOB must be greater than 120°; if 
AOB is less than 120° the sector XOY 
will be dead space. This can be shown 
as follows: 

Placed at the point O the rifleman 
will cover with his fire: 

(a) The sector of 60° perpendicular 
to the crest OA. 

( b ) The sector of 60° perpendicular 
to the crest OB. 

These sectors are equally divided by 
the normal line, hence the angles MOA 
and NOB are angles of 60°. There¬ 
fore : 

(a) The beaten sectors for riflemen 
at O are 120° + 120° = 240°. 

( b ) In order for O and OY to coin- 



























Field Fortification 


29 


cide, and the dead space to disappear, 
the angle AOB must be at least 120°. 
When the terrain is such as to necessi- 


( a ) Indented line (Fig. 60) : 

( b ) Redan trace (Fig. 61) : 

( c ) Tenailled trace (Fig. 62), if the 



tate giving AOB a value less than 120°, 
the point of AOB should be cut off 
(Fig. 56), so as to get two larger angles, 



equal to at least 120°. Moreover, flank 
fire produces great effect and counter¬ 
balances numerical inferiority, so that 

k 

i 

♦ 

i 
i 


Fig. 58. 

traces must be made which will permit 
this fire. 

29. The three types of traces are the 




T=_l 




15 L 

Fig. 60. 


line of fire is broken, with two adjacent 
crests mutually flanking each other, the 
trace is called tenailled. 



Fig. 61. 

( d ) Bastioned traces (Fig. 63), if 
the two flanks face each other and give 
a reciprocal flank fire, the trace is called 



Fig. 62. 


bastioned: HGABC is a bastion; AB, 
EF are faces; BC, ED are flanks; CD 
is the curtain. 

The wings of a trench are always 



Fig. 63. 



lunette (Fig. 57) ; the flattened lunette 
(Fig. 58) ; and the redan (Fig. 59). 

30. In tracing intrenchments, combi¬ 
nations of these types are generally 
adopted, as follows: 


terminated by flanks which give a flank 
fire upon the interval which separates 
it from its neighbor. 

PART V 

CONSTRUCTION OF TRENCHES. 

31. Composition of working groups: 

Experience has shown that the best 
method of dividing up the work (the 
men being furnished with park tools) 
is to group the men in pairs; one with 












30 


Field Fortification 


a pick, the other with a shovel; and to 
prescribe that they relieve each other. 
The length of the task is determined by 
laying the picks and shovels down along 
the trace as shown in Fig. 64. 

The length of the task corresponds to 
the length of fire crest necessary for two 
men; the workers alternating with pick 
and shovel have periods of relative rest. 

32. Work done by a working group: 

A man unaccustomed to digging, in 
continuous work, can only dig his task a 
depth of 1 foot an hour; a depth of 2 ft. 
4 in. an hour can be quickly obtained by 
making frequent reliefs and exacting 


"if 


ffQ-- 

li 


ir 

Jl-—, 

r iL 


Fig. 64.—Tasks marked out by tools, a, b, c, 
d, e,f, g\ stakes marking the trace. 

the maximum of effort during the work, 
so that a standing trench can be con¬ 
structed in a minimum time of two 
hours. 

The average work of a group of two 
men not relieved is 1 ft. 4 in. an hour; 
that is, the deepening will be 1 ft. 4 in. 
an hour and the standing trench will be 
completed in a minimum time of three 
hours. 

33. Method of executing the work: 
When the tactical situation permits ex¬ 
ecuting the work in safety, the following 
method is adopted: 

(a) Establish the trace, place the eye 
at the level of the interior crest (1 ft.). 
Mark out the trace with stones or 
stakes. Mark the points of change of di¬ 
rection (maximum 120°). Mark the po¬ 
sition of each traverse, between squads 
(minimum thickness of traverse, 2 
yards). 

( b ) Deploy the working party along 


the trace by such method as the tactical 
conditions demand. 

(c) Place the rifles and packs on the 
rear side, the rifles in reach. 

( d ) Mark out the tasks on the 
ground with a pick. Mark out the tra¬ 
verses in the same manner. 

( e ) Strip the sod from the width of 
excavation (3 ft. 4 in.) and rapidly con¬ 
struct with it a mask or small parapet, 
with a steep slope on the rear; raise it 
to 1 ft. 4 in. (The piling up of the earth 
on it will reduce it later to 1 ft.) 

(/) Dig as vertically as possible. 
The slope must not exceed 10 / 1 , except 
around the traverses, where it may be 
increased to 15 / 1 or 20 /i- As soon as the 
parapet affords sufficient protection, the 
workers, designated beforehand, make 
the traverses. They are commenced at 
the two ends. 

(g) Make a parados as soon as the 
depth exceeds that for a kneeling 
trench (2 ft. 4 in.). 

( h ) Conceal the trench by means of 
sod taken previously from the sites of 
the parapet and parados and give to 
these the appearance of the original 
ground. 

(i) Arrange communications masked 
from view (by brush, etc.). 

( k ) Proceed to the individual and 
collective arrangements. 

34. Night work: 

When circumstances render night 
work necessary, special dispositions 
must be made: 

(a) Except where absolutely impos¬ 
sible, stake out the trace before com¬ 
plete darkness. 

( b ) If the trace can only be fnade at 
night, utilize visible reference points 
(white paper, white stones, white tape, 
pocket lamps, etc.). 

OTFor the distribution of the work 













Field Fortification 


31 


and commencement of it, employ the 
same principles as for day work. 

( d ) Avoid, except the inevitable 
noise of the tools, anything that may re¬ 
veal the presence of the workers (cig¬ 
arettes, conversation, etc.). 

( e ) Protect the workers by patrols 
stationed to the front. 

35. Methods of measuring: 

When the work is done in safety, the 
greatest care should be taken to make it 
as accurately as possible. It is particu¬ 
larly necessary to see that the typical 
dimensions are followed out to within 
2 inches, and these should be checked 
with rods upon which these dimensions 
are marked, or by comparison with the 
following lengths: 

4 in. Width of the hand. 

6 in. Width of the blade of the Ord¬ 
nance portable intrenching shovel 

(6 “As in-)- 

8 in. Width of the blade of the E.D. 
small size shovel in regt. tool wagon 

(834 in.)- 

1 ft. Length of the blade of the E.D. 
small size shovel (11 in.). 

1 ft. Length of the foot of a man. 

1 ft. 8 in. Total length of the Ord¬ 
nance portable intrenching shovel 
(21 y 2 in.). 

1 ft. 8 in. Total length of the bay¬ 
onet (20.6 in.). 

2 ft. 8 in. Total length of the E.D. 
pick mattock in regt. tool wagon (33 
in.). 

5 ft. Total length of rifle with bay¬ 
onet fixed. 

These lengths should be thoroughly 
taught to the infantryman, for they are 


necessary for the proper construction of 
intrenchments; and he will know that 1 
ft. 8 in. is not 1 ft. 4 in. and he will 
always have the dimensions of his firing 
trench, communication trench, and shel¬ 
ter in his mind; he will know before¬ 
hand the length of his task, and will not 
dispute over its execution. 

conclusion. 

36. It is difficult to realize what the 
organization of a fortified point costs in 
methodical labor and blood, when it is 
accomplished under the fire of hostile 
artillery, and small arms. Under the 
direct rifle and machine-gun fire, and the 
intermittent shower of shell and shrap¬ 
nel, the working party continues, mak¬ 
ing as little noise as possible and hiding 
as best they can, to dig into the ground, 
place the stakes, put up the barbed wire, 
and strengthen the advanced trenches. 
There are no words to describe the long 
night hours during which the workers 
complete, in this way, the system of fire 
trenches, arrange for sure communica¬ 
tion with the rear, and place the obsta¬ 
cles which the enemy will next day en¬ 
counter. Suddenly a machine gun 
opens fire; all lie down and crawl into 
their holes. The alarm has been given 
in the hostile position; the fusillade com¬ 
mences, the rockets go up; great lights 
go up and light the ground. The hostile 
look-outs redouble their vigilance. It is 
necessary to wait until the enemy’s ac¬ 
tivity ceases, and then again the 
workers glide to their posts to fix the 
stakes, and, tirelessly, to complete the 
protecting system. 




CHAPTER III 


THE TRENCH WEAPONS. 

The present war in Europe has 
shown that, when the direct fire of 
powerful modern arms becomes in¬ 
effective, the combatants return to the 
weapons and machines of ancient war¬ 
fare. Grenades, abandoned for a 
hundred years, and catapults, slings, 
onagers, etc., are now in use. Grenades 
appear to have been first used in 
1516, at the siege of Arles. The city 
was threatened with investment; a great 
quantity of grenades which the defen¬ 
ders were to use in throwing from the 
top of the walls among the assailants 
were sent there. The grenades were made 
of glass, globes, jars, kegs, and fire- 
pots. In 1677, at the siege of Stettin, 
the defenders used grenades attached 
to rods, which were fired from muskets, 
although the regular method was to 
throw them by hand or by means of a 
shovel. Regiments of grenadiers were 
formed, but, at the end of the seven¬ 
teenth century, as the fire of infantry 
became predominant, grenades were 
given up. 

Machines, such as catapults, slings, 
onagers, etc., are known to have been 
used eight centuries b.c. The Bible 
tells us that the walls of Jerusalem were 
provided with “ machines constructed 
by a very wise engineer to throw bolts 
and large stones.” 

At the present time rapid-fire 
weapons having forced opposing armies 
to entrench, warfare has become a long 
siege with frequent sorties. Under 
these conditions, the grenade has be- 
32 


come very useful, both on the offensive 
and the defensive. Its effects are spe¬ 
cially useful at the moment of assault, 
when by its deadly explosions, follow¬ 
ing the violent artillery preparation, 
it completes the demoralization of the 
defenders of the hostile trenches. 

2. Grenades may be classified, ac¬ 
cording to their range, into: 

(a) Hand grenades, with range of 
30 to 35 yards. These may be explosive 
grenades, suffocating grenades, poison- 
gas grenades, tear-producing gren¬ 
ades, incendiary or smoke-producing 
grenades. 

(5) Rifle grenades, with a range of 
80 to 200 yards. 

(c) Grenades, or bombs, for trench 
weapons. 

PART I. 

HAND GRENADES, RlELE GRENADES, AND 
TRENCH WEAPONS. 

3. Explosive hand grenades are made 
up of a case containing a certain quan¬ 
tity of explosive. As regards ignition, 
they are divided into two types: percus¬ 
sion and time. Some are a combination 
of the two, and have both time and 
percussion fuses. As regards tactical 
employment, grenades are also divided 
into two classes: defensive, relying 
upon fragments of bullets; and offen¬ 
sive, relying upon the blast of high 
explosive. 

4. Handling and Transportation.— 
Great precautions should be taken in 
the handling and transportation of 
grenades. They are always dangerous, 


Field Fortification 


33 


especially when handled by men igno¬ 
rant of their make-up or assembly. For 
transportation, they should be carefully 
packed, with the fuses in separate 
boxes. They should be protected from 
dampness, and the fuses should be kept 



FIG. i. 

entirely separate from the explosive 
cases. The safety devices should never 
be removed until the moment of 
throwing. 

5. Grenade Throwing .—The instruc¬ 
tions for priming and throwing of each 
type should be carefully followed. 
Grenade work should be rapid, but 
without hurry, with calmness and cool¬ 
ness. The grenade should be thrown 
immediately after its fuse is ignited, 
even when there is some doubt whether 
it has been properly ignited. Men 


should be carefully and thoroughly 
trained in grenade throwing. Their 
use by trained men greatly reduces the 
risk of accidents and the expenditure 
of grenades. The proper method of 
throwing is shown in Figures 1 to 5. 

Initial position (Fig. 1) : Aim at 
target with the extended left arm. With 
the grenade in the right hand, the right 
arm falls naturally alongside the body. 
The shoulders, the extended left arm, 
and the target should be in the same 
vertical plane. 



FIG. 2. 


First motion (Fig. 2) : Left arm 
maintained in the direction of the tar¬ 
get. Carr}' the grenade to near the left 
hand for igniting. 

Second motion (Fig. 3) : Left arm 
maintained in the direction of the tar- 





34 


Field Fortification 


get. Carry back the right arm by 
swinging it in the vertical plane, eye 
following the grenade to avoid hitting 
it against anything in rear. Extend the 
left leg, bending over right leg. 

Third motion (Fig. 4) : Look again 



fig. 3 . 

at the target, or at the aiming point if 
there is one in the trench. 

Fourth motion (Figs. 5-a, 5-b) : With 
the right arm, describe an arc of a circle 
in a vertical plane, the right shoulder 
and the body following the movement 
of the arm. Extend the right leg, bend 
the left leg. The left arm is swept vig¬ 
orously through the air following the 
left shoulder, which is refused. 

The grenade thrown vigorously 
in this way will go in the direction 
toward which the left arm is aimed. 


The right arm acts like a catapult. It 
should never be thrown horizontally nor 
with the elbow bent. The fire must be 
plunging. The duration of the execu¬ 
tion of the four motions is about two 
seconds. 

6. Training in grenade throwing 
should have the following objects in 
view: 

(a) To teach every infantry unit so 
that it can rapidly undertake a grenade 
fight when circumstances demand it. 

(b) To train selected squads to exe¬ 
cute sudden grenade attacks. 



fig. 4 . 


The squad should be organized into 
a squad leader, two riflemen, two gren¬ 
ade throwers, three ammunition 
bearers. It may be followed by a chain 
of men to pass forward ammunition, 
and a squad of pioneers. As soon as 




Field Fortification 


the first line of the enemy is reached, 
the grenade fighting commences. In the 
trenches and approaches there will 
always be angles and traverses that 
must be cleared of the enemy. 

7. The typical method of trench clear¬ 
ing is shown in Fig. 6. The enemy 



FIG. 5A. 

must be driven back step by step, and 
a formation adopted that will minimize 
the losses caused by his grenades. A 
rifleman (f 1 ) acts as a point, stops the 
enemy’s approach, and protects the 
grenade throwers. Two grenade 
throwers (l 1 , l 2 ) throw grenades to 
points 1, 2, 3, then to 1', 2', 3', always 
beyond the defiladed spaces, and so as 
to assure a constant and progressive 
clearing out of the trench. The squad 
leader ( Ch ) directs the fight, corrects 
the fire, organizes the relief of the 
grenade throwers and of the ammuni¬ 
tion bearers, superintends the ammuni¬ 


35 


tion supply, and prepares to defend his 
ground foot by foot if progress becomes 
impossible. The three ammunition 
bearers (p 1 , p 2 , p 3 ) are stationed several 
paces in rear so that they can get out 
of the way without stumbling over each 
other. They pass up the grenades in 
bags. A chain of men passes up the 
ammunition from the nearest grenade 
depot. A squad of pioneers ( P ) is 
stationed close in rear of the ammuni¬ 
tion bearers, ready to construct a barri¬ 
cade or to demolish those of the enemy. 
They are supplied with shovels, picks, 
empty sand-bags, bombs, and explos- 



FIG. 5B. 

ives. They may also have rifle gren¬ 
ades to interfere with the enemy’s am¬ 
munition supply, and one or two men 
with automatic rifles to defend the 
barricades. 

The grenade squad must preserve 
silence and observe carefully all noises 
coming from the enemy. When the 




36 


Field Fortification 


leading group decides that the enemy is 
overwhelmed, the first rifleman creeps 
forward carefully in the smoke, peeps 
around the angle, and signals to his 
comrades. Thus they progress from 
turn to turn and from traverse to tra¬ 
verse. The squads must not bunch up; 
not more than three men should be 
together; they must advance prudently 
and watch for traps, fougasses, etc. 
The long, straight portions of trench 
are often enfiladed by rifles or machine 
guns placed in the traverses. The 


ferent duties and be ready to under¬ 
take them at once when ordered by the 
squad leader. 

On open ground, grenade squads 
march in the formation of patrols. 

8. Rifle Grenades .—A well-directed 
fire of rifle grenades demoralizes the 
enemy and causes much more severe 
losses than an artillery bombardment. 
The enemy’s trenches should be care¬ 
fully observed to ascertain the points 
where men are likely to be stationed, 
such as sentry posts, entrances to 


ppp r chU-r ^v 



Principal Boyau B. 
Fig-6. 


enemy also hides at the end of a blind 
lateral trench, the entrance of which 
is masked by a piece of painted canvas. 
If the advance is made too rapidly, the 
enemy comes out of his hiding place 
behind the grenade squad and cuts it off. 

When a lateral trench is reached 
( B '), several grenades should be 
thrown in both directions, at least three 
at each traverse, as shown at b 1 and b 2 . 
It should be explored and barricades 
established and guarded if it is not con¬ 
sidered necessary to continue farther 
along it. 

All the members of a grenade squad 
should be able to perform all the dif- 


shelters, intersections of approaches, 
etc. Rifles clamped in racks should be 
directed at these points, in order that a 
grenade may be fired at them immedi¬ 
ately upon the indication that they are 
occupied. Fire should be continued 
night and day at these points. In spite 
of the almost complete concealment of 
the enemy, his dispersion, and his pro¬ 
tection by shelters, it will be possible 
to inflict appreciable losses upon him by 
a constant rifle grenade fire, directed 
at well-chosen points. 

A well-directed rapid fire by small, 
perfectly-trained detachments, upon an 
enemy assembled for attack, or upon 

















































Field Fortification 


37 


known and registered points of the 
communications, at the hour of chang¬ 
ing reliefs, should give excellent results. 

In assaults, the employment of men 
carrying rifle grenades should be 
closely coordinated with the other ele¬ 
ments of the attacking lines. 

In trench clearing, the fire of rifle 
grenades should be carefully executed 
by the supply squad which follows im¬ 
mediately in rear of the squad of gren¬ 
ade throwers. This fire should inter¬ 
fere with the enemy’s supply and bar 
his lines of retreat. 

The range of rifle grenades is about 
200 yards at an angle of 45 degrees. 
The angle of fall is large, and makes 
their fire against trenches very effective. 
The rifle may be fired from the shoulder 
or from a special rack. 

9. Trench weapons are divided into 
two general classes, viz., high power, 
which are handled by the artillery, and 
low power, whose propelling power is 
powder, compressed air, or springs 
handled by the infantry. Only the low- 
power weapons will be discussed. 
These are organized into batteries of 
four to six pieces and attached to bat¬ 
talions. The assignment of the weap¬ 
ons among the different battalions of 
the regiment is made so as to concen¬ 
trate the maximum number at the most 
important points, with a view to the re¬ 
sults to be obtained. 

10. Tactical Employment of Trench 
Weapons. —Low-power trench weapons 
have a range which varies from 50 to 
300 yards, according to the propelling 
charge and the setting of the time fuses. 
They are not very effective against 
materiel, but are very effective against 
personnel sheltered behind cover which 
gives protection from rifle fire. 

On the offensive, they may be 
employed: 


(a) Against works, such as machine- 
gun emplacements, nearly demolished 
by the artillery preparation, which the 
enemy, having been sheltered in deep 
bombproofs from this fire, has reoccu¬ 
pied. 

( b ) In parts of the front adjacent to 
those from which the offensive has 
started, with a view to supporting the 
attack in conjunction with the infantry 
remaining in the trenches and which 
has been reduced to a minimum; and in 
order to neutralize the corresponding 
hostile front and prevent hostile action 
against the flank of the attacking 
troops. 

(c) After a successful attack, by 
moving forward to the captured front, 
and there rapidly organizing emplace¬ 
ments for its defense or for action 
against portions of the new hostile front 
which are too near to permit artillery 
fire against them, without danger to 
our own troops. 

On the defensive, trench weapons 
may be employed: 

(a) On parts of the front held by a 
few men where the effects of these 
weapons will compensate for the small 
garrison. 

( b) On parts of the front which are 
close to hostile listening posts, small 
posts, or advanced works which threaten 
the first line. 

(c) Behind the first lines, close to the 
second or third line of a position, with 
a view to making untenable parts of a 
line captured by the enemy. 

11. Location of Emplacements. —The 
location depends primarily upon the ob¬ 
jective. The fire has the most effect 
when it is oblique; but, in the first line, 
observation of the fire is easiest and the 
fire is more accurate. The emplace¬ 
ments are therefore located near the 
first line, preferably in parts of the line 



38 


Field Fortification 


most difficult for the enemy to reach, 
such as re-entrants, defiladed points, etc. 
Three or four alternative emplacements 
should be constructed on each line of 
trench ; and the emplacements for a bat¬ 
tery should be divided by traverses into 
positions for a platoon of two guns. 

12. Fire of trench weapons is divided 
into four classes: 

(a) Destructive fire: Against listen¬ 
ing posts, small posts in course of con¬ 
struction, and blockhouses already dam¬ 
aged. This fire must be rapid. 

(b) Offensive fire: At the time of the 
preparation for an attack, by adding to 
the artillery fire. 

(c) Defensive fire: Rapid fire upon 
the parallels of an enemy, preparing 
for an attack; rapid, sudden, and unex¬ 
pected fire at opportune times upon 
trenches and approaches captured by the 
enemy. 

( d ) Firing in periods of calm: This 
must be very rapid at any time that the 
enemy appears negligent; such as a 
working party arriving in a trench and 
observed from an elevated observing 
station; during a calm following a vio¬ 
lent fight; during the hot hours of the 
day, during rain, during dark, silent 
nights, etc. 

The commander of a battery of trench 
weapons must be constantly on watch 
and alert; and he must cooperate to the 
highest degree to give an aggressive atti¬ 
tude to the garrison of a sector during 
the periods of calm. 

Trench weapons may throw either 
hand grenades or special projectiles. 

PART II. 

PRINCIPLES OE THE EIRE OE TRENCH 
WEAPONS. 

13. Definitions. 

The trajectory is the curve followed 
by the projectile (Fig, 7). 


The range is the distance AB between 
the weapon ( A ) and the point of fall 
(B), (Fig. 7). 

The angle of fire is the angle “ a ” 
formed by the direction of the weapon 



with AB, which joints the weapon and 
the target (Fig. 7). 

The angle of site is the angle which 
this line makes with the horizontal 
(Fig. 8). 

The inclination of the trench weapon 



* i ” is the sum of or the difference be¬ 
tween the angles of fire and of site, 
according as B is above (Fig. 8) or be¬ 
low (Fig. 9) the horizontal. 

The angle of fall is the angle that the 
trajectory makes with the horizontal at 



greater than the angle of fire. 

The initial velocity is the velocity of 
the projectile at the muzzle. 

The plane of defilade is the plane 
passing through the upper part of 
the mask or cover which protects the 







Field Fortification 


39 


emplacement and through the point 
from which it is desired to be defiladed. 
Points situated above this plane are 
visible from the latter point, those below 
are hidden from it. 

14. Classification of fire. 

According to the angle of fire: 

(a) Direct fire: Corresponding to a 
flat trajectory, for which the angle of 
fire is less than about 15 degrees. 

(b) Plunging fire: Corresponding to 
the curved trajectory, for which the 
angle of fire is greater than 15 degrees. 

(c) Vertical fire: If the angle of fire 
is greater than or equal to 45 degrees. 



With a given initial velocity, there are 
two angles of fire which permit hitting 
the same target. These two angles of 
fire, in the case of an angle of site equal 
to zero, and not taking into account the 
resistance of the air, correspond to two 
directions symmetrical with respect to 
the line at 45 degrees, so that the sum of 
the two angles is 90 degrees. 

Example: If the point B (Fig. 10) 
can be reached from the point A with 
an elevation of 20 degrees, the other 
angle permitting a hit on the same point 
with the same initial velocity is 70 de¬ 
grees. In reality, the movement of the 
projectile being made through air, a 
slight correction must be applied to the 
above rule ; this correction depends upon 
the projectile employed. 

According to the direction of fire: 


(a) Direct fire: Normal to the crest 
of the hostile entrenchment. 

(b) Oblique fire: Oblique to the crest 
of the hostile entrenchment. 

(c) Enfilade fire: Parallel to the crest 
of the hostile entrenchment. 

(d) Oblique reverse fire: Oblique to 
the crest and coming from the rear. 

(e) Normal reverse fire: Normal to 
the crest and coming from the rear. 

15. Classification of Trench Weapons. 
—Trench weapons generally use plung¬ 
ing fire; they may be divided into two 
general classes, viz.: 

Of constant initial velocity: 

(a) Powder charge constant, in the 
case of mortars. 

(b) Constant tension of springs, in 
the case of spring weapons. 

(c) Constant air pressure, in the case 
of pneumatic weapons. 

Variation in the range is obtained by 
variation of the angle of fire. As there 
are two angles of fire that correspond 
to the same range, the greater of the two 
is generally used to obtain plunging fire. 
The variation of the angle is not pro¬ 
portional to the variation of the range. 
To determine the range, having given 
the angle of fire, or conversely, the fir¬ 
ing table for each weapon is used. This 
may be in the form of a table from 
which the range may be read ofif for any 
angle; or in the form of a curve, where 
the abscissae indicate the ranges and the 
ordinates the corresponding angles 
(Fig. 11). Example: The range of 75 
meters corresponds to the angles of 20 
and 70 degrees. 

In this class are included trench 
weapons which are able to give to the 
projectiles a limited number of initial 
velocities, by changes in the charges or 
pressures. The above rules are applied 
to each of the initial velocities. The fir¬ 
ing tables are of double entry. The 





40 


Field Fortification 


graphical firing tables contain several 
curves, each corresponding to a well- 
determined initial velocity. 

Of constant angle of fire; the initial 
velocity is then variable: 

(a) Powder charge variable. 

( b ) Tension of spring variable. 

( c ) Air pressure variable. 

A single initial velocity corresponds 
then to a given range. It is generally 



given by a firing table in tabular form. 
Weapons of this character generally 
permit two inclinations: usually 45 de¬ 
grees and 60 degrees. To each of these 
inclinations corresponds an initial ve¬ 
locity given by the firing table. 

16. Adjustment of Fire.— The ad¬ 
justment of fire consists in finding the 
elements which cause the projectile to 
hit the target. It is divided into two 
operations: adjustment in direction 
and adjustment in range. 

(a) Adjustment in Direction .— 
Trench weapons do not usually have 
devices for adjustment in direction. A 
device may be improvised as follows: 
Trace on the ground, with their inter¬ 
section directly under the vertical axis 
of rotation of the weapon, two right 
lines perpendicular to each other, one 
of which is parallel to the trench; divide 
each of the right angles into 16 equal 


angles (Fig. 12). A peg should be 
placed at each division at the same dis¬ 
tance from the center, and should be 
numbered from 0 to 32, as indicated in 
the figure. Each of the angles thus 
obtained equals one-tenth, i.e., the angle 
that subtends 10 yards at a distance of 
100 yards, or 5 yards at a distance of 
50 yards. When the scale is to be used 
for some time, it should be made on a 
plank platform. 

(b) Adjustment in Range. —This is 
obtained by variation of the angle of 
fire or of the elements which vary the 
initial velocity. A constant use of the 
firing table is necessary. The range is 
obtained by bracketing the target be¬ 
tween two shots, one short, the other 
long, corresponding to two ranges, 
slightly different. As trench weapons 
have short range and are very accurate, 
a very small bracket may be used, from 
two to five yards. The chief of the 
piece or observer must give for each 
modification the new elements of fire 
for range (angle of fire, charge, pres¬ 
sure, tension) according to the reading 
of the firing table. 


Trench 



F«g. 12 

17. Principles of observation. 

(a) Observation for Direction.—In 
order to accurately observe the direction 
and amount of deviation in azimuth of 
a shot, the observer must be in the plane 
of fire of the weapon. If not in this 
plane, considerable errors may be made, 
when the error in range is great; as an 














Field Fortification 


41 


error in range may be taken for one in 
direction. 

(b) Observation for Range.—The 
adjustment of the fire for range depends 
upon an accurate observation of the 
points of fall of the projectiles. If the 
smoke of the explosion hides the target, 
the range is too short. If the terrain on 
which the target lies slopes toward the 
piece, the shot is short or long according 
as the point of fall is seen under or over 
the target. When it is difficult to ob¬ 
serve errors of range from a point in the 
plane of fire, these errors must be deter¬ 
mined by an observer placed well to one 
flank of the piece. 

PART III. 

DESTRUCTION OF UN EXPLODED 

GRENADES. 

18. After each drill in throwing 
loaded grenades, those that have not 
burst should be destroyed. If the gren¬ 
ades have time fuses, at least ten min¬ 
utes should elapse from the time the 
last grenade was thrown before anyone 
is allowed on the range to hunt for un¬ 
exploded grenades. These grenades 
may then be considered harmless, and 
they may be gathered and placed in a 
small pit and exploded with a small 
charge of high explosive placed in the 
Center of the pile. The detonation can 
be made more complete by placing sev¬ 
eral shovelfuls of earth over the pile of 
grenades. Before the charge is ex¬ 
ploded, the personnel should be under 
shelter. 

If the grenades have percussion fuses, 
it is dangerous to move them, and they 
should be destroyed with a small charge 
of high explosive placed in contact with 
them and covered carefully with a 
shovelful of earth. In case of a misfire, 


ten minutes must elapse before the oper¬ 
ation is repeated. 

It must be absolutely forbidden for 
anyone to try to unprime unexploded 
grenades by unscrewing the fuse. 

CONCLUSION. 

19. In all sectors of the Western 
Front in Europe, the grenade throwers 
have shown great skill and the advan¬ 
tage of thorough instruction. 

In one instance, the French succeeded 
in occupying the entrance of one of the 
principal avenues of a village; the Ger¬ 
mans held the rest. The houses that 
lined this avenue were practically de¬ 
stroyed ; some pieces of the walls alone 
remained standing. The Germans, skil¬ 
fully hidden in the shelter of the ruins, 
had stopped the French charge, and had 
brought up a field gun and placed it 
behind a barricade so that it enfiladed 
the avenue. It was impossible to de¬ 
stroy the gun with artillery, so that 
grenade throwers were sent forward to 
destroy it. After two hours of slow 
and stealthy approach under constant 
rifle fire, they succeeded with several 
well-placed grenades in killing the can¬ 
noneers just as they were, loading the 
gun, and were able to capture it. The 
riflemen who followed them were then 
soon able to capture the rest of the 
avenue. 

During the numerous attacks at Ver¬ 
dun the grenade throwers covered them¬ 
selves with glory. The engagements 
inside Fort Douamont were among the 
most exciting and most tragic of the 
war. When the details of the fighting 
at Vaux, Thiamont, and Fluery are 
known, the great value of the work 
of the grenade throwers will be 
appreciated. 




CHAPTER IV 


PROFILE AND EXECUTION OF DELIBER¬ 
ATE field WORKS. 

1. General Principles. —Field fortifi¬ 
cation is divided into hasty or light, and 
deliberate. The directing principles are 
the same in both cases. The first de¬ 
velops into the second when the stay in 
one position is long enough to permit 
improving and completing the work 
executed at first in haste. 

The strengthening of light field 
works, which were constructed under 
conditions explained in the preceding 
lecture, will have for its object: 

(1) To increase the resistance to hos¬ 
tile artillery. 

(2) To increase the protection of¬ 
fered to the occupants. 

(3) To create sheltered communica¬ 
tions: (a) With the elements of ob¬ 
servation and advanced defense. ( b ) 
With the neighboring elements of the 
firing line, (c) With the rear, for sup¬ 
ply, evacuations, command posts, rein¬ 
forcements, etc. 

(4) To place under shelter the per¬ 
sonnel and apparatus for observation, 
illumination, and communication. 

(5) To create shelters for the mate¬ 
rial, arms, ammunition, and emplace¬ 
ments and shelters for machine guns 
and trench weapons. 

(6) To better living conditions in the 
trenches. 

(7) To make the approaches to field 
works very difficult for the enemy. 

Part I 

increase of resistance of trenches 
to artillery fire 

2. Deepening the Trench. —The first 
step in strengthening the trench is to 


deepen and widen it. In this way are 
obtained : 

a. The earth necessary for the 
strengthening of the parapet. 

b. The space necessary for the revet¬ 
ment of the walls of the trench. 

A minimum depth is 6 feet 8 inches; 
width at the top, 4 feet 8 inches; width 
at the bottom, 3 feet 4 inches. 



The work is progressive—from the 
rear part of the complete trench, the 
part hachured in the drawing is exca¬ 
vated. An intermediate step permits 
the rifleman to reach the firing ban¬ 
quette. 

3. Increasing the Strength of the 
Parapet. —There is no longer any diffi¬ 
culty about increasing as much as possi¬ 
ble the thickness and height of the para¬ 
pet which protects the riflemen. Its 
strengthening is secured by the employ¬ 
ment of sand-bags and by the construc¬ 
tion of loopholes whose base should be 
at a maximum height of 5 feet. 

4. Revetment of the Walls of the 
Trench. —Resistance to the destructive 
effects of fire on the trenches should be 
increased by revetting the walls of the 
trench. This can be done in several 
ways: from the light revetments de¬ 
scribed in the preceding lecture to the 
construction of walls of reinforced con- 


42 




Field Fortification 


43 


crete (Fig. 3). The proportions of ce¬ 
ment, sand, and gravel or broken stone 
most used are (a) one of cement, two 
of sand, and five of gravel or broken 
stone; and ( b ) one of cement, three of 
sand, and six of gravel or broken stone. 
Steel rods are used for the reinforce¬ 
ment. 



Fig. 2.—Arrangement to cause 
projectiles to burst. 


5. Arrangements to Cause Projectiles 
to Burst. —At night narrow trenches 
may be dug in the parapet, which are 
filled with a layer of logs. These will 
cause a premature burst of projectiles 
which hit in front of it (Fig. 2). 

6. Concrete Revetment. —By gradu¬ 
ally increasing the amount of concrete, 
the work approaches the character of a 



Fig. 3.—Concrete revetment. 


permanent fortification. The interior 
walls may be revetted with concrete 
walls, and concrete traverses may be 
constructed at intervals of two or three 
yards. Steel loopholes may be placed, 
and a recess constructed in the front 
wall which will form an excellent shel¬ 
ter (Fig. 3). 


Part II 

increase; of protection for the 
PERSONNEL/ 

7. Protection of the Personnel in the 
Firing Trench. —The trace should be a 
broken line, with traverses, splinter 
proofs, individual niches for the rifle¬ 
men, and bomb-proofs with armored 
roofs. 

8. Traces of Broken Lines. —The 
greatest danger against which it is 
necessary to protect the personnel is 
that of enfilade fire. The best means of 



protecting is to avoid traces of long, 
straight lines. When under fire it is 
not always possible to construct tra¬ 
verses at first, and they must often be 
constructed later. They may be re¬ 
placed by: 

a. Using a trace of a broken line 
(Fig. 4). 

b. Using an indented trace (Fig. 5). 

The perpendicular distance between 

the axes of the longer straight elements 
should not be less than 5 feet, and these 
elements should not be longer than 6 
yards. 



9. Traverses. —The best method for 
defense against enfilade fire is to local¬ 
ize the effect of projectiles by employ¬ 
ing traverses (Figs. 6, 7, and 8). 









44 


Field Fortification 


To give protection against the effect 
of heavy artillery, the traverse must be 
at least 2 yards thick on top. In places 
exposed to direct fire, this thickness 



must be increased to 3 or 4 yards, de¬ 
pending upon the character of the soil. 
In depth, the traverse should project at 
least one yard beyond the face of the 
rear wall of the trench. The interval 
between traverses should be from 6 to 8 
yards. In exposed places this interval 
should be reduced to 4 or 5 yards. 

10. Traverses Constructed after the 
Completion of the Trench .—If prac¬ 
ticable the traverses should be con¬ 
structed simultaneously with the trench. 
If, however, the trench has been made 
without traverses, they should be COn- 


fAbe 

- S“ -- 0 - 



structed as soon as practicable by ob¬ 
structing a part of the trench with sand¬ 
bags, boxes, barrels, gabions, etc., and 
a passage should be opened around them 
to the rear. When the traverses are 
wide, berms should be constructed on 
the sides, and a firing banquette should 
be constructed for flanking fire. This is 
especially necessary on the flanks of a 
trench and at the exits of a communi¬ 
cating trench. 


11. Individual Niches. — In places 
particularly exposed to enfilade fire, in¬ 
dividual niches for riflemen should be 
constructed between the traverses 

(Fig- ?)• 

These afford efficient protection 
against enfilade fire. They are often 
constructed in old trenches which have 
been damaged by projectiles or bad 
weather. 

12. Splinter Proofs. — In trenches 
greatly exposed to artillery fire, splinter 



Fig. 8.—Perspective of 
traversed trench. 


proofs should be constructed between 
the traverses. Their roofs should be 
just thick enough to protect against 
shell fragments and shrapnel, and they 
should be short so as to reduce as little 
as possible the length of the fire crest. 
They may be constructed of fascines, 
sand-bags, or gravel and sand between 
two layers of planks. 



Fig. 9.—Splinter proof. 


A form of splinter proof which can 
be readily constructed is shown in Fig. 
9. It is made by driving stakes into the 






















Field Fortification 


4 5 


parapet; on these are placed poles and 
a layer of earth a foot thick. If steel 
rails are available they may be used in¬ 
stead of the stakes and poles, and afford 
much better protection. The supporting 
rails should be braced by props set in 
the rear berm of the trench, and loop¬ 
holes should be constructed. 

The trench may be covered as shown 
in Fig. 10. Parts of the trench should 



Fig. 10.—Covered trench. 


be left uncovered—one for a section of 
each company—to enable troops to 
leave the trenches for an attack. The 
dimensions of the trench are not 
modified. 

If sufficient logs are available, a 
double roof may be constructed (Fig. 



11). Two layers of logs with a foot of 
earth between form a cover capable of 
resisting a 150 mm. (5.9 in.) high ex¬ 
plosive shell. 

A covered trench with an open pas¬ 
sageway (Fig. 12) may be constructed 
from the standing trench by widening 


the trench. It forms an excellent con¬ 
tinuous shelter and does not interfere 
with an advance or render the defenders 



Fig. 12.—Covered trench with passageway. 


liable to be bottled up, as does the cov¬ 
ered trench shown in Fig. 10. The pro¬ 
tection can be increased by increasing 
the number of traverses and making in¬ 
dividual niches of gabions, fascines and 
sand-bags (Fig. 13). 



Fig. 13.—Covered trench with individual 
gabion traverses. 


13. Head Cover .—Head cover is the 
term applied to any horizontal cover 
which may be provided above the plane 
of fire. It is obtained by notching or 
loopholing the top of the parapet. 

(1) Notches .—When the relief of a 
trench is too great for a man to fire 
standing, or when the height of the 
parapet is more than a foot above the 
level of the ground, notches should be 
made in the parapet. The simplest way 
to make these and give support to their 
sides and make them the least visible 
is to arrange sand-bags on top of the 
parapet as shown in Fig. 14. 













46 


Field Fortification 



Fig. 14.—Sand-bag notches. 


(2) Loopholes. — When overhead 
cover is used, loopholes are necessary. 
They may be collective, as shown in 
Fig. 10, or individual, constructed of 
sand-bags, wood, steel, hurdles, etc. 


Fig. 14a.—Loopholes of sand-bags. 

a. Loopholes of sand-hags. —These 
can be rapidly constructed, afford good 
protection and are easily concealed. 
Their strength can be increased by us¬ 
ing planks or light poles under the sacks. 
About sixteen sand-bags are required to 
a loophole. 

b. Steel and wooden loopholes .— 
These should be prepared in the rear. 
They require 9 to 10 square feet of 



Fig. 15.—Side 
of a wooden 
loophole. 


boards, 1 to V/2 inches thick, and 40 
nails, 2 to 3 inches long. Two carpen¬ 
ters can make a loophole in an hour. 
Steel plates decrease the visibility and 
greatly increase the protection. They 
should have an opening with a movable 
cover, and should be placed at the rear 
of the loophole. 

c. Loopholes of hurdles. — When 
boards or steel plates are not available. 


loopholes may be constructed or hurdles 
or woven brush. The dimensions 
should be the same as those shown in 
Fig. 16. 



Fig. 16.—A wooden loophole. 


d. Loopholes of steel rails. —These 
may be constructed of two pieces of rail, 
not more than a foot long, placed ver¬ 
tically at an angle to each other, with 



Fig. 17.—Loop¬ 
holes of steel 
rails. 


an interval of an inch or two for firing 
through. The webs of the rails may be 
reinforced with 3-inch wooden strips to 
prevent bullets penetrating, and blocks 
should be used to hold the rails apart. 
Pieces of rail may also be used to form 
a narrow, horizontal opening, an inch 
or two high. 



Fig. 18.—Loophole of 
folding gabion. 


e. Loopholes of folding gabions 
(Fig. 18).—The folding gabion is made 
of boards hinged together. They can 
be formed into parallelograms of differ¬ 
ent angles and thicknesses and are very 
convenient for making loopholes: 






















Field Fortification 


47 


(3) Shields .—These are of two 
kinds, the portable and the parapet. 

a. The portable shield (Fig. 19) is 
intended for fighting in the open, but 
may be used on a parapet. It is made of 
special steel, 20 inches square and .33 
inch thick; weighs 33 pounds, and will 
resist an ordinary bullet at short range. 



Fig. 19.—Portable 
shield. 


It has a loophole, two folding feet, and 
four holes for the attachment of a car¬ 
rying cord. The cord can be arranged 
so that the shield can be carried on the 
arm when under fire, or on the back 
when not under fire. 

b. The parapet shield is specially 
made for use as a loophole, but it can 
be utilized when crawling forward (Fig. 
20). It is made of special steel, 2 feet 



Fig. 20.—Parapet shield. 


4 inches by 1 foot 4 inches and .43 to 
.47 inch thick; weighs 66 pounds, and 
will resist an armor-piercing bullet at 
all distances. It has a rectangular loop¬ 
hole 2 by 3 y 2 inches. When these 
shields are assembled on the parapet, 
they should be placed from 1 to 2 feet 
apart (Fig. 21), one in front of the 


other, and the loopholes connected with 
wooden boxes covered with sand-bags 
or earth. 



Fig. 21.—Parapet shield assembled. 


c. Shields of steel, or wood and sand, 
or gravel (Fig. 22) can be made of a 
thickness to resist bullets (see Lecture 
I, Part IV). Loopholes or notches 2 
by 3j/ 2 inches should be made on the 
fire crest, at intervals of a yard. 



Fig. 22.—Combination shield. 


An individual shield of steel and 
sand, 2 feet by 1 foot 4 inches, can be 
made with steel sheets .12 inch thick. 
They are bound with angle iron, which 
is also used to form stakes (Fig. 23). 
Two sheets are fastened 2 inches apart 



Fig. 23.—Individual shield. 


with wooden strips between them, and 
the space filled with sand. They are 
bullet proof at a distance of 10 yards. 






























48 


Field Fortification 


14. General Remarks on Head Cover. 

a. It should be concealed by using 
grass, brush, canvas, empty sand-bags, 
etc. 

b. The sky as a background should 
be avoided by raising the parados or 
placing a canvas curtain behind the rifle¬ 
man’s head and closing the opening 



Fig. 24.—Arrangement for fire over parapet. 


with a cover which can be removed 
when the loophole is in Use. 

c. In addition to its visibility, head 
cover has the disadvantage that it 
causes a pause in the fire of the de¬ 
fender when the attack reaches the most 
deadly zone of fire, because the de¬ 
fenders have to withdraw their rifles 
to prepare for bayonet fighting. It is 
therefore necessary to arrange for fire 
over the parapet. For this purpose ban¬ 
quettes can be constructed of sod, stone, 
logs or scaffolding between the loop¬ 
holes (Fig. 24). 

d. In some sectors the loopholes have 
their axes inclined to the normal. 



Fig. 25.—Loophole placed obliquely. 


e. Every loophole intended for ob¬ 
servation should be placed obliquely in 
the parapet in order to be protected 


against shots from the front (Fig. 25). 

/. In some sectors loopholes should 
not be used at all. 

15. Shelter under the Parapet .— 
These shelters for rest and protection 
against artillery fire can be rapidly and 
easily constructed (Fig. 26). 

They must: 

a. Not interrupt the line of fire. 

b. Be capable of execution after the 
trench is finished. 

c. Permit a rapid sortie. 

They should be about 3 feet 4 inches 
wide, 5 feet high, and 6 feet 8 inches 
long; and will shelter from 6 to 8 men. 
The overhead covering should be at 
least 3 feet 4 inches plus the height of 
the parapet. In earth they should be 
lined. Wooden steps should replace the 



1 

Fig. 26.—Shelter under parapet. 


firing banquette, which must be re¬ 
moved in excavating the shelter. 

PROTECTION FOR THE PERSONNEL IN THE 
IMMEDIATE VICINITY OE THE FIRING 
TRENCH 

16. During a heavy bombardment 
which renders the trenches untenable, 
the personnel must be sheltered so that 
it will be available at the moment of as¬ 
sault. For this purpose shelters should 
be constructed with logs, earth, steel 
rails, concrete, and by sinking them 
from 25 to 40 feet under solid ground. 





















Field Fortification 


49 


To limit the effects of hits, only small tance of 10 to 12 yards from the fire 
shelters should be used. Their maxi- trench. 

mum capacity should be from one to 17. Cave Shelters under the Parapet. 
three squads. In the first line there —The advantage of these is due to the 



must be a number of shelters so that the 
men who must be kept there under the 
most violent fire will be completely 
sheltered. In the rear lines and in the 
communicating trenches it is necessary 
to have numerous strong shelters for 


fact that they can be located close to the 
fire trench (Figs. 27, 28 and 29). The 
protection can be increased by placing a 
layer of steel rails on the surface of the 
ground to cause projectiles to burst. 
Two entrances should be provided, as 



the large garrison that must be stationed 
there. 

These shelters should be constructed 
on branches from the fire trench or 
from a communicating trench, at a dis- 


they are liable to be obstructed by cav¬ 
ing in. The entrances should not be 
placed on opposite side of a traverse, as 
a hit on it might obstruct both entrances. 
Observation from them may be pro- 




















































50 


Field Fortification 


vided by boring a hole with an earth 
auger to the surface of the ground, in 
which a periscope can be used. Venti¬ 
lation is obtained in the same way. As 
the shelters are liable to cave in, espe¬ 
cially at the entrance (picks and shovels 
should be stored in them and arrange¬ 
ments made for their ventilation. 

18. Shelters in Rear of the Fire 
Trench. —These must be situated so 
that the personnel sheltered in them can 
man the firing crest in the minimum of 
time. They are on branches from the 
communicating trenches, immediately 
in rear of the fire trench, or on special 
trenches constructed for the shelters 
(Figs. 30 and 36). 



Fig. 30.—Plan of shelters on the communi¬ 
cating trench immediately in rear of the 
firing trench. 


a. On the communicating trench im¬ 
mediately in rear of the firing trench,— 



Fig. 31.—Plan of a shelter. 


This trench is usually from 10 to 12 
yards in rear of the firing trench and is 
called the circulating trench. The di¬ 
mensions of the shelter, the height of 
the ceiling, and the arrangement of the 


woodwork are shown in Figs. 31 to 35 
By reducing the height of the ceiling, 
the height of the earth thrown out on 



each side of the communicating trench 
is diminished. The normal height of 
the ceiling is 6 feet; as the height of the 
earth thrown out must not exceed 2 feet 
to 2 feet 4 inches and as the depth of 
the communicating trench is from 5 feet 
4 inches to 6 feet 8 inches, the level of 
the floor of the shelter will be at 7 feet 
10 inches. Drainage should be provided 



for by constructing a drainage pit. 
One, or better, two entrances should be 
constructed from the communicating 
trench, and the shelters should be con¬ 
nected if possible. The ceiling beams 
should be given as much bearing as pos¬ 
sible on the side towards the enemy, and 
on each side about a yard. To protect 
the ceiling against the effects of blast, 
the logs should be bound together with 
cross pieces, held together with wire. 



























































Field Fortification 



which should be fastened to stakes 
firmly driven into the ground. 



Fig. 34.—Details of 
construction. 


The posts and caps should be con¬ 
nected with iron straps and bolts as 
shown in Fig. 34. 

A more rapid but weaker method of 
construction is shown in Fig. 35. A 



Fig. 25.—Rapid 
construction. 

good method of resisting lateral pres¬ 
sure is very important. 

The walls of the shelter should be re¬ 
vetted by the methods described in th? 
second lecture. 


for the shelters .—In certain sectors, 
deep shelters are arranged . on both 
sides of a special communicating trench 
constructed for that purpose (Fig. 36). 

This communicating trench is situ¬ 
ated between the fire trench and the cir¬ 
culating trench. Their construction is 
similar to that of shelters under the 
parapet of the firing trench. They pos¬ 
sess certain advantages for the proper 
supervision and assembling of the per¬ 



Fig. 36.—Plan of shelters constructed on a 
special communicating trench. 

sonnel sheltered. The trench is com¬ 
pletely covered where the shelters are 
constructed, and the covering is made 
up of successive layers of logs and 
earth (Fig. 37). 

c. Cave shelters .—Cave shelters are 
constructed by the methods used in 
military mining. They are placed from 
25 to 30 feet under solid ground, and 
are used for the first lines and for 
strong points. They should be supplied 



Fig. 37.—Details of shelters constructed on a special communicating trench. 


For ventilation, heating, drainage, and with material, ammunition and rations 
protection again asphyxiating gas and for several days. They are also used 
caving in of the walls, see paragraph 21. to shelter the command posts (par. 52) 

b. On special trenches constructed of all units. The dimensions vary ac- 























52 


Field Fortification 


cording to the garrison and use (Figs. 
38-40). 

Their height should be at least 6 feet 
8 inches, width 10 feet, length variable, 
but their capacity should under no cir- 



Fig. 38.—Cross-section of a cove shelter. 


cumstances exceed that for three squads. 
The men sheltered should be able to get 
complete rest. Two tiers of cots or 
hammocks should be arranged against 
the walls. There should be two en¬ 
trances, covered in the communicating 
trench by rifle or machine-gun fire from 
a traverse blockhouse (par. 21). 



Fig. 39.—Plan of a shelter cove. 

The framework and sheathing of the 
shelters and the galleries for entrance 
are constructed in accordance with the 
methods of military mining described in 
the sixth lecture. 


The shelter shown in Figs. 39 and 40 
is intended for a garrison of 25 men. 
Of these 2 would be on watch and 6 on 
picket duty, leaving 17 men off duty. 
For these there are 16 cots 6 feet by 2 
feet 4 inches, arranged injtiers as shown, 
and a space at the right for the com¬ 
mander. Hammocks may be used in¬ 
stead of cots; they leave more space 
and are more comfortable. 

By reducing the size of the shelter to 
a length of 20 feet, width 6 to 8 feet, 
height 6 to 8 feet, 18 men can be shel¬ 
tered, 8 lying down and 10 standing. 

At the upper end of the entrance gal- 



Fig. 40.—Cross-section of a cove shelter and 
entrance gallery. 

lery there should be a niche, with a loop¬ 
hole for a man on watch. 

PROTECTION OP THE PERSONNEL IN REAR 
OP THE PIRST LINES 

19. Shelters for the Reserves in¬ 
tended for counter attacks, rest shelters 
in the zones in rear exposed to the bom¬ 
bardment of heavy artillery, are organ¬ 
ized in accordance with the preceding 
principles. However, it is possible to 
utilize more fully the natural features 
of the terrain such as steep slopes, 
sunken roads, quarries, etc.; cellars of 
houses, and the concealment and pro¬ 
tection of woods and forests. The con- 







































































Field Fortification 


53 


struction can be made stronger as there 
are more time, more materials and 
workmen available, and a relative secur¬ 
ity due to invisibility. 



Fig. 41.—Shelter constructed on a steep slope. 


a. Shelters utilizing natural features 
of the terrain (Figs. 41-45). 

b. Shelters utilizing the cellars of 
houses. —The cellars should be con- 



Fig. 42.—Shelter constructed in a deep de¬ 
pression of the ground. 

nected by underground passages. The 
arches on the first floor should be cov¬ 
ered with a thick layer of sand-bags, 



Fig. 43. — Shelter con¬ 
structed in a sunken road, 
utilizing a pile of rock. 


and a floor constructed to cause projec¬ 
tiles to burst. Ventilation should be 
carefully arranged and protected. Nu¬ 
merous exits must be provided for lat¬ 
eral communication and to the rear. 
All unnecessary openings should be 
strongly closed to prevent the entrance 
of projectiles. 



in a quarry. 

c. Shelters in woods (Figs. 46 and 
47).—The height of these shelters and 
the quantity of material required make 



Fig. 45. — Shelter constructed in a 
sunken road, utilizing a line of trees. 


this construction possible only in woods. 
Alternate layers of logs and earth for 
the walls and roof afford protection 
from fire. The dimensions are variable, 
but they should provide cots or ham- 















54 


Field Fortification 


mocks for 25 to 30 men. The cots are 
6 feet by 2 feet 4 inches, constructed 
with a frame of wood covered with 
wire netting. 



in woods. 

20. Methods of Strengthening Shel¬ 
ters .—When a position is occupied for 
considerable time, the shelters may be 
strengthened by a proper combination 
of wood, broken stone, steel and con¬ 
crete. A covering of 1 foot 8 inches 
of concrete affords protection against 
direct hits of the 105 mm. (4.13 inch) 
field howitzer; of 3 feet 4 inches, against 
those of the 130 mm. (5.12 inch) and 
150 mm. (5.9 inch) mortars; of 6 feet 
8 inches, against the 210 mm. (8.27 



Fig. 47.—Cross-section of a shelter 
in woods. 


inch) mortar. By reinforcing the con¬ 
crete with steel bars, steel rails, and 
wire mesh, the resistance is greatly in¬ 
creased. Concrete should be poured 
over a layer of steel rails or logs for the 
roof, and the walls and floor should be 
similarly concreted. 

a. Roof of earth and steel rails with 
an intermediate layer of stone (Fig. 48). 


—The rails are placed on heavy sills 
such as cross ties (Fig. 51), side by side 
and firmly fastened together with wire. 
A second layer is added if practicable, 
or a layer of earth from 1 foot to 2 feet 
thick, then a layer of broken stone 2 
feet thick, and on top a second layer of 
earth from 2 to 3 feet thick. The total 
thickness of the cover should be from 
5 to 7 feet. 

b. Roof of timber, earth and an in¬ 
termediate layer of broken stone (Fig. 
49).—This roof consists of two or three 



Fig. 48.—Roof of earth, broken stone and 
steel rails. 


layers of timber. Between these are 
placed layers of earth, 12 inches thick, 
to deaden shock. An intermediate layer 
of broken stone, with concrete poured 
over it if possible, greatly increases the 
protection. It has little height above the 
ground, affords great protection, and 
can replace cave shelters. 



Fig. 49.—Roof of earth, timber and broken 
stone. 



































Field Fortification 


55 


c. Roof of earth, broken stone, con¬ 
crete and steel rails (Fig. 50).—This 
kind of shelter is specially suitable for 
the protection of assembly places near 
the first lines. The trench is broken by 
traverses 8 feet 4 inches thick and 5 



Fig. 50.—Roof -of earth, broken stone, 
concrete and steel rails. 


yards apart. The rails should be at 
least 8 yards long for the longitudinal 
layer and about 3 yards for the trans¬ 
verse layer. They will then have bear¬ 
ing of 4 y 2 feet on the traverse on each 
side. It is important to provide a proper 
bearing for each layer of rails, not only 
on the traverses but also on the front 
side of the trench. 



Fig. 51.—Detail of 
arrangement of steel 
rails. 


d. Shelter of corrugated iron. —Cor¬ 
rugated iron is neither proof against 
bullets nor the fragments of artillery 
projectiles or those of trench weapons, 
but it can be used to support the thick¬ 
ness of the earth which gives the neces¬ 
sary protection. Its great advantage is 
that, with it, the construction of the 


shelter, once the excavation is finished, 
is rapid and easy. 

21. General Remarks on Shelters. 

a. Security. —A shelter is only valu¬ 
able when it affords protection to the 
garrison and is so arranged that they 
can leave it promptly in case of an at¬ 
tack. Its roof and walls should be 
thick enough to resist penetration of the 
projectiles fired against it (see the sec¬ 
ond lecture, where the required thick¬ 
ness of various materials is given). 

In order that the garrison may leave 
it promptly in case of attack, there must 
be a look-out placed to one side of the 
shelter in a protected niche, sunk into 
the parapet, concealed and furnished 
with means to communicate with the 
shelter to give the alarm; if the means 
of communication is interrupted, the 
look-out must leave his post. 



To give the garrison time to get out. 
even if the enemy be actually in the 
trench, it is necessary to construct 
traverse blockhouses at intervals. These 
should cover the exit of the shelter and 
its vicinity (Fig. 52). The firing posi¬ 
tion communicates with a shelter for 
several men with rifles or automatic 
rifles, who can enfilade the trench. The 
blockhouse is constructed of rails and 
concrete. Besides the positions for the 
look-outs, a certain number of shelters 
should be provided with means for 
using long periscopes from the inside 


















56 


Field Fortification 


(Fig. 40). When an attack is ex¬ 
pected the officers and noncommissioned 
officers remain in the shelter with their 
men. 

b. Arrangements to cause projectiles 
to burst. —As has already been ex¬ 
plained in paragraph 5 for the parapets, 
and in paragraph 17 for cave shelters 
under the parapet, the protection of the 
personnel can be greatly increased by 
causing projectiles to burst in front of 
the shelters by using layers of logs, or 
above the shelters by using steel rails in 
the roofs. 

c. Protection from rain. —Rain-water 
filters through all soils, especially 
through loose earth that has been 
placed over the shelters. Protection is 
secured by placing, on one layer of 
logs, roofing paper, corrugated iron, tin 
or zinc, linoleum, canvas, tiles, etc. 



Fig. 52a.—Ventilation 
arrangement. 


d. Drainage. —It is necessary to pro¬ 
vide drainage for water which runs 
into the shelter through the entrance or 
seeps through the walls. A pit should 
be dug near the entrance and the floor 
of the shelter should be sloped towards 
it; the pit must be emptied when 
necessary. 

e. Ventilation and protection against 
asphyxiating gas. —Ventilation is se¬ 
cured by boring vertical or inclined 
holes with an earth auger through the 
roof. These can also be used for peri¬ 
scopes (Figs. 40 and 52). Against 
asphyxiating gas it is necessary to her¬ 


metically seal the shelter as soon as the 
alarm is given. For this purpose two 
curtains of canvas or blankets are 
placed at the entrance, a certain dis¬ 
tance apart. There must always be a 
barrel of a solution of hyposulphate of 
soda in the shelter, which should be 
sprayed into the air. 



Fig. 53.—Plan of heating system. 


/. Protection against caving in of the 
walls. —The walls should be revetted by 
the methods described in the second lec¬ 
ture. Picks and shovels should be 
stored in the shelter so that the garri¬ 
son can dig their way out; an earth 
auger should also be available so that 
ventilation can be secured and a hole 
made rapidly for food and water to be 
passed into the shelter. There should 
also be stored in the shelter, food, am¬ 
munition, grenades and rockets to warn 
the lines in rear. 

g. Heating is provided by cast iron 
stoves, or, if stoves are not available, 
by braziers placed in niches below the 
level of the floor of the shelter and at 



Fig. 54.-r-Cross-sectioii of 
heating system. 





























Field Fortification 


57 


one end of it (Figs. 53 and 54). If the 
shelter is long, the flue is carried 
through its length so as to get the max¬ 
imum of heat. This pipe is made by a 






Fig. 55.—Flue made of tiles. 


trench 3 by 5 inches covered with tiles 
(Fig. 55). The tiles should be ar¬ 
ranged as indicated in the figure, with 
reference to the direction of the smoke, 
and the joints should be calked with 



Fig. 56.— Fig. 57. —Flue 
Flue of of tin or iron 
pipes. sheets. 


clay; or by using stove pipe, drain pipe, 
or gas pipe (Fig. 56) ; or with sheets of 
tin or iron to cover a trench (Fig. 57). 
The pipes are banked with tamped earth 
to keep them in place. 


Part III 


construction of sheltered commu¬ 
nications 

22. General Principles .—It is neces¬ 
sary to communicate with ease, rapidity 
and security: 

a. Toward the front with the ad¬ 
vanced elements of observation, such as 
small posts, listening posts, etc. 

b. Laterally with the adjoining ele¬ 
ments of the firing line. 

c. Toward the rear with the food 
and ammunition depots, the command 
posts, and the reserves. 

A distinction can be made, according 
to the length of occupation of the posi¬ 
tion, between improvised communica¬ 
tions and sunken communications. The 


first belong to light field fortifications; 
they are arranged rapidly with the main 
object of screening the movements of 
troops from the view of the enemy, as 
there is not time enough to shelter them 
from fire. In woods this is easily se¬ 
cured, but it is necessary to place sign¬ 
boards for use during the day, and lan¬ 
terns at night, which will indicate the 
routes to be followed. 

Lateral communications .—A commu¬ 
nicating trench with a firing crest, pro¬ 
tected with barbed-wire entanglements, 
should connect the centers of resistance, 
thus forming a continuous line of 
trenches and preventing the enemy pen¬ 
etrating between the strong points. 

Communications to the front and 
rear .—These connect up the successive 
lines of trenches. They should be pro¬ 
tected on both sides by barbed-wire en¬ 
tanglements. Some are arranged for 
firing and are provided with a firing 
banquette and elbow support. 

23. Ordinary Communicating 
Trenches (Fig. 58).—The relief must 
not be less than 6 feet; it is usually 6 
feet 8 inches. They should be con¬ 
cealed as much as possible by making 
the parapets not more than 1 foot 4 
inches to 2 feet high, and giving them a 
flat slope and rounded crest. The earth 
should be spread out and the exterior 
slope of the parapets made uniform so 
that grenades that fall on it will roll 
away from the trench. There should 
be a berm of about a foot on both sides 
to: 

a. Prevent the earth from falling into 
the trench and making it muddy. 

b. To form a small platform for 
tools, packs and rifles, and to give more 
space for two columns to pass each 
other. 









Field Fortification 


58 


c. To permit infantrymen with 
packs to leap over the trench. 

When water or rock is near the sur¬ 
face it is necessary to make the parapets 



higher, and in some places no trench can 
be dug and parapets must be made 
of gabions, sand-bags, etc. 

The width varies with traffic through 
it, but it should be at least 3 feet 8 

H»V) 



Fig. 58a.—Communicating trench. 

inches at the top and 3 feet at the bot¬ 
tom. The bottom of the trench should 
be constructed and maintained slightly 
convex for drainage, or a ditch, filled 



Fig. 59.—Communicating trench with 
single fire crest. 


with small stones, should be constructed 
on both sides. To allow troops to move 
in column of twos the width should be 
increased to at least 5 feet; for the 
movement of vehicles such as artillery 


and supply wagons it should be 8 feet 
4 inches. In this case the relief should 
be increased to from 9 to 10 feet. The 
trench should be widened by 2 feet 8 
inches to 3 feet 4 inches at certain dis¬ 
tances to permit men to pass each other. 

24. Communicating Trenches Ar¬ 
ranged for Firing (Figs. 59 and 60).— 
When it is necessary to arrange for fir¬ 
ing on one or both sides, as the parapet 



Fig. 60.—Communicating trench with 
double fire crest. 


already has a height of at least 1 foot 1 
inches, it is usually raised to 2 feet; and 
as the relief for firing must not exceed 
5 feet a banquette at least 3 feet below 
the surface of the ground must be Con¬ 


or*) . 

}*.H.***~2| •• 


r wr> 






Fig. 61.—Stepped trace. 




















Field Fortification 


59 


structed. If it is undesirable to widen 
the trench for this purpose, wooden 
benches may be stored in passing places 
so that they can be set in place rapidly 
when it is desired to open fire. 

25. Trace .—When the construction 
of communicating trenches is hurried 
and they are not traced with stakes and 
compass, they are usually given a trace 
with gentle curves, which do not pro¬ 
tect from enfilade fire and cannot be de¬ 
fended by flank fire. • The only traces 
that should be used are: (a) the stepped 
(Fig. 61) ; ( b ) the traversed (Figs. 62 
and 63), both of which are easy to con- 



trace. 

struct and to defend; and (c) the zig¬ 
zag (Fig. 64), which gives better defi¬ 
lade and provides numerous flanking 
elements. 

The stepped and traversed traces are 
preferable for approaches that are used 
for bringing up men and supplies, as 
they are shorter; the zigzag trace is bet¬ 


ter for the evacuation of wounded, as 
the litters can be carried around the 
turns easier. The angle between two 
branches should not be less than 30 de¬ 
grees in order not to make the length 
of the trench too great. The longer 




;^pn'iww pppm# 








Fig. 63.—Island traverse. 


branches of the stepped and traversed 
trenches should not have a length greater 
than 10 yards in order to defilade it; the 
short branches should be at least 4 
yards long, so as to project at least 2 
yards beyond the longer branches. 

The zigzag trace is executed in the 
following manner: 

a. The direction of the approach be¬ 
ing determined by a line NM, give to 
the first branch ab a length of 4 to 6 
yards, and an inclination of 30 to 45 de¬ 
grees, and place the middle of the cord 



























60 


Field Fortification 


representing the exterior edge of the 
trench on the line MN at a point x 1 . 

b. Then lay off on MN the distances 
x v x 2 , x 2 x 3 , etc., equal to double the dis¬ 
tance of x 1 from the front edge of AD. 
Place stakes to mark these points. 

c. Two men placed at the ends of the 
cord ab alternately stretch the cord from 
b to c and the man on the right places 
the stake c when the cord be, stretched, 
is in contact with x 2 . 

In the same way, the man on the left 
places the stake d where the cord held at 
c, and stretched, passes the stake x 3 . 

i ** 
i 



Fig.—Z igzag trace. 


d. Then join the points a, b, c, d and 
outline at 3 feet 4 inches or 3 feet 8 
inches the trace of the interior edge of 
the trench. Round off the angles. 

Continuity of the trace (Fig. 65).— 
A part of a parallel should never be used 
as part of an approach, as DABC. Be¬ 
sides causing confusion it renders 
passage through the approach difficult 
when the parallel is occupied by troops. 
It should be remembered that the rate 
of travel through an approach is that at 
its most difficult point, such as at a 
tunnel under a road, a bridge, water 


hole, etc. A connecting trench, as AC, 
should be dug. 

Trace at the angles. —Whatever form 
of trace is used, the passage around the 



angles in the trace should be easy and 
permit the passage of litters for 
wounded, especially in the approaches 
for the evacuation of the wounded. 
This result is obtained in the following 
manner: 



a. For obtuse angles, round off the 
reentrant angle and blunt the salient 
angle (Fig- 66). 

b. For right and acute angles, widen 
or round off the angles (Figs. 67 and 
68 ). 

26. Execution. —When sheltered from 
the enemy’s fire, or at a distance, or at 









Field Fortification 


61 


night, the approaches are constructed 
in a manner similar to the construction 
of trenches as explained in the second 



lecture. Work at night is specially 
recommended. 

Under fire of the enemy, when it is 
necessary to join the first lines with 
elements of a captured trench, with a 



Fig. 68.—Trace at acute angle. 


listening post, or with a mine crater, the 
methods of sapping or the methods of 
mining described in the Engineer Field 
Manual are used according to the cir¬ 
cumstances. These methods are de¬ 
scribed in the sixth lecture. 

,27. Tracing—The. construction of an 
approach should be preceded by care¬ 
fully staking it out with careful meas¬ 
urements. The measurements are 
necessary in order to secure economy of 
time and to permit the clear formula¬ 
tion of orders for the conduct and com¬ 
pletion of the work. 

28. Signposts. —At all branches there 
should be placed in each branch two 
solid signposts, planted firmly in the 


berm beyond reach of accidental blows 
and in a niche where a lantern can be 
placed, and placed so that they will at¬ 
tract the attention of men passing in 
either direction. The approaches should 
be named, and these names should be 
kept all the way through, as they con¬ 
stitute important reference lines in 
maps of the defenses. Besides sign¬ 
posts, the principal approaches are dis¬ 
tinguished from the minor ones by 
making them from 1 foot to 1 foot 4 
inches deeper at all forks or crossings. 

29. Stairs, Storage Places, Foot¬ 
bridges, Niches. — Frequent storage 
places and steps for leaving the ap¬ 
proaches should be provided. Steps are 
also necessary at the crossings of other 
approaches or parallels; these are used 
at night, with a foot-bridge over the 
principal approach. By providing two 
stairways, the rate of march through 
the approach will not be decreased 
much. Foot-bridges may be constructed 
over all the trenches which cross an im¬ 
portant approach, and these, with a path 
parallel to the approach, may be used at 
night in order to supplement the ap¬ 
proach and lessen the time required to 
reach the front. 

There is a tendency to dig, by indi¬ 
vidual initiative, shelters and niches in 
the approaches; this tendency should 
be repressed. Everything tending to 
cause a halt, hence loss of speed, must 
be prohibited. An approach should be 
kept absolutely clear, and nothing 
should open into it except other ap¬ 
proaches. 

30. Bridges over the Approaches .— 
These should be constructed in proper 
places, with a layer of logs. 

31. Covered Approaches— On par¬ 
ticularly exposed points, the approaches 
should be covered with splinter-proof 









02 


Field Fortification 


roofs, constructed according to the prin¬ 
ciples of the roofs of shelters, as previ¬ 
ously described. 

32. Dispositions for Defense .—The 
lateral communicating trenches and the 
approaches can in certain cases be ar¬ 
ranged like firing trenches and can be 
protected by barbed-wire entangle¬ 
ments. They assist thus in the defense 
of the front and in the flanking disposi¬ 
tions for the intervals between the sup¬ 
porting points. 

Moreover, the approaches should be 
organized so that they can be defended 
by rifle, grenade and machine-gun fire 
over every foot, and they should be ar¬ 
ranged so as to trap the enemy if he 
should get into them. 

The dispositions for defense by rifle 
and machine-gun fire can be organized 
at a distance from or at one end of a 
straight line of approach. If the rifle 
or machine gun is placed at a distance 
to facilitate the fire, sections 1 yard in 
length will be removed from the para¬ 
pet of the approach. Sometimes it will 
be necessary to cut away part of the 
side of the approach. At the end of a 
straight line of approach the arrange¬ 
ment will comprise a small firing trench, 
a yard long, provided with one or two 
loopholes and with a position for a 
grenade thrower immediately behind the 
firing trench (Figs. 69 and 70). 



Fig. 69.—Cross-section of an arrangement 
for the defense of an approach. 

The traps will consist: 

a. In making island traverses or 
blind approaches, and of placing false 
walls on the opening of one of the two 


trenches around the traverse. The en¬ 
emy having passed the island traverse, 
or opening of the blind approach, will 
be at the mercy of the defenders hid¬ 
den in the part concealed from view. 



Fig. 70.—Plan of arrangement for the de¬ 
fense of an approach. 


b. In closing with a false wall the 
opening of a shelter where the de¬ 
fenders can act in the same way. 

c. In making, outside the approach 
and in its immediate vicinity, holes 
where defenders can be hidden who can 
isolate advanced hostile groups. 

d. In making false approaches which 
rise gradually to the ground level. 
When the heads of the enemy appear, 
riflemen posted in a proper position can 
shoot them down. 

33. Maintenance .—The trenches and 
approaches, after prolonged use, dete¬ 
riorate, not only from the fire of the 
enemy but also from the effects of the 
weather. They must constantly be re¬ 
paired. Walls which break down must 
be revetted. Firing banquettes must be 
constantly repaired with planks, fas¬ 
cines, etc. Damaged parapets must be 
repaired. Berms must be kept at 
proper width. Drainage pits must be 
watched carefully and kept cleaned out. 
It requires constant work to keep the 
trenches clean and sanitary. Any com¬ 
mander who tolerates lack of work or 
poor work under any pretext is wanting 
in the first duty of a commanding 
officer. 

























Field Fortification 


63 


When parts of trenches or approaches 
are captured, steps must be taken imme¬ 
diately to clear them of insects which 
swarm there and transmit disease 
germs, particularly typhus. Straw 
should be burned in the trenches and 
shelters, and all wood should be white¬ 
washed. 

Part IV 

CONSTRUCTION OF SHELTERS FOR OBSER¬ 
VATION, ILLUMINATION AND COMMU¬ 
NICATION 

34. Observation. — The observation 
of the enemy is of first importance in 
position warfare. It should give com¬ 
plete knowledge of all the elements of 
the hostile line and prompt information 
of any movement of the enemy. It is 
effected by observation from the ground 
and observation by aircraft. 

Observation from the ground is di¬ 
vided into three echelons: 

a. Observation in front of the first 
line from small posts and listening 
posts. 

b. Observation on the first line by 
sentinels and lookouts. 

c. Observation in rear of the first 
line by artillery observers, sentinels, and 
lookouts of the shelters. 

It is effected by the infantry and 
artillery. 

35. Observation in Front of the First 
Line .—The small posts or listening 
posts of from 1 to 8 men are placed in 
rifleman’s pits, shot holes, organized 
shell craters or in short semicircular 
elements of trench, connected with the 
first line by sap or low mine gallery. 
Their protection is assured by their in¬ 
visibility. The retreat of the observers 
is protected: 

a. By a system of branch galleries 


whose entrance into the main gallery 
can be rapidly closed. 

b. By a barbed-wire protection placed 
over the sap. 

The look-outs in small posts are 
placed in very short trenches, which are 
provided with loopholes. Protection at 
short range against grenades is secured 
by a network of wire. 

36. Observation on the First Line .— 
This is effected by look-out posts or¬ 
ganized preferably at the salients where 
the view is more extended. These posts 
give a view over the enemy’s first line. 
They are provided with periscopes, with 
range finders, and large scale maps. 

a. Simple hole in the parapet .—It 
will often be sufficient to pierce a cir¬ 
cular opening in the parapet with a 
stick or to place a pipe in it. 

b. Armored shelters and sentinel 
boxes .—These are provided by the en¬ 
gineer park and can be put into posi¬ 
tion without further preparation. The 
shelters have four sides and shelter 


r, 

I 



Fig. 71.—Observer’s post of sheet steel and 
sand-bags. 


only the head of the observer. The sen¬ 
try boxes are cylinders large enough to 
shelter the entire body of the look-out. 
They are made of special steel, .47 inch 
thick, of reinforced concrete, or of 
double steel walls .12 inch thick with a 






64 


Field Fortification 


space of 4 inches filled with gravel or 
well-packed earth. 

c. Shelter of sheet steel and sand¬ 
bags (Figs. 71, 72, and 72a).—The shel¬ 
ter is formed with a caisson of sheet 
steel. Two box-like receptacles on the 
front face are filled with gravel. The 
upper part is strengthened by a layer 
of logs and a covering of earth. The 
lateral part in rear is covered with sand 
bags. The front face is bullet-proof; 
the side walls protect from oblique fire 
and the roof from the burst of projec¬ 
tiles. A similar shelter can be impro¬ 
vised from materials available if spe- 

A 



Fig. 72. —Plan through A-B. 

daily prepared steel sheets are not on 
hand. 

d. Shelter of steel rails and sand-bags 
(Fig. 73).—An easy type to improvise 
is shown in Fig. 73. Two steel rails, 2 



Fig. 72a.—Plan through E-F. 

feet 8 inches in length, are placed hori¬ 
zontally a few inches apart, parallel to 
the trench. Upon these is constructed 


a roof to protect against the burst of 
projectiles. A frame protected by sand¬ 
bags covers the rear. 



Fig. 73.—Observer’s post of rails and 
sandbags. 


e. Concealment of look-out posts .— 
It is necessary to conceal these posts by 
all possible means. Observation is car¬ 
ried out under good conditions only 
when it is done without the knowledge 
of the enemy. The posts should prefer¬ 
ably be constructed on the right of a 
traverse, and in an excavation in front 
of the trench wall (Fig. 74). 




✓ 







Fig. 74. —Location of an observer’s post. 


37. Observation in Rear of the First 
Line. —The observation posts, even of 
the infantry, are not necessarily in the 
first line trench or in the listening posts. 
Often, in the rear, points will be found 
which will give an excellent view and 
will not attract the enemy’s attention. 
The term “observatory” is often em¬ 
ployed for this kind of observation 
post. 

The observatory generally has a more 
extended view than the look-out’s post; 
it is protected and has means of com¬ 
munication such as telephone, helio- 









































Field Fortification 


65 


graph, messengers, carrier pigeons, 
wireless. It may belong to the infantry, 
the artillery, or the higher commands. 
The observatory may be occupied by 
the commander himself or by an ob¬ 
server who represents him. In any case 
the observatory is near the command 
post. It is only useful so long as it can 
resist bombardment, therefore must 
have a low parapet, be defiladed from 
view, and proof against the large pro¬ 
jectiles. A good form consists of a steel 
sentry box, sunk into a mass of concrete 
or placed at the end of a sap. They 
must be provided with large periscopes. 
Their construction must be made with 
the greatest care, the excavated earth 
removed to some distance, the position 
concealed, etc. It is a good idea to 
make false observatories, relatively visi¬ 
ble, at some distance from the real ones. 

38. Coordination of Observing Sta¬ 
tions. —The location of the look-out 
posts and observatories must be deter¬ 
mined in accordance with a complete 
plan for each center of resistance or 
sector of defense. No part of the hos¬ 
tile front should be free from observa¬ 
tion, and the parts of the front favor¬ 
able for the attack of the enemy should 
be specially watched. An observatory 
should be located near the combat posts 
of the commanders of the supporting 
points, centers of resistance and sectors. 
The observatories of centers of resist¬ 
ance and of sectors must have extended 
views over the whole of the terrain. 

39. Illumination of the Battlefield .— 
In position warfare it is necessary: 

a. To discover and keep in touch with 
the movements of the enemy during the 
night. 

b. To seek out and illuminate hostile 
objectives so as to fire upon them. 

c. To blind the enemy. 


These results are obtained with 
searchlights. The smaller ones, about 
12-inch, are acetylene, and have a short 
range. The larger, about 24-inch, are 
electric and have a longer range. They 
can also be used for signaling. They 
are placed in shelters, similar to those 
for machine guns, located so as to flank 
the line of fire (Figs. 75 and 76). 



Fig. 75.—Plan of a searchlight shelter. 

They can also be placed in rear of the 
first line on a platform with no overhead 
cover; but the personnel should be pro¬ 
tected by a shelter close to the platform, 
from which the searchlight may be oper¬ 
ated. The generating apparatus should 
be placed in rear under a strong shelter. 



Fig. 76.—Searchlight shelter, cross-section 
A-B. 


40. Communication. —During a bom¬ 
bardment communication becomes very 
difficult, but it must be maintained by 
all possible methods. This may be ac¬ 
complished by: 

a. Installing telephones under strong 
shelters. 
























Field Fortification 


(>() 


b. Using lead covered cable, buried 6 
feet deep, especially for the lines con¬ 
necting the regimental, brigade, division 
and corps headquarters. 

c. Placing rockets in all shelters and 
observatories where officers or noncom¬ 
missioned officers are posted. 

d. Preparing posts for visual signal¬ 
ing, safe from bombardment and defi¬ 
laded from view of the enemy. These 
posts are constructed in shelters similar 
to those for searchlights and are pro¬ 
vided with horizontal loopholes with the 
opening to the flank or rear. 

Part V 

DEPOTS POR MATERIAL, AMMUNITION 

AND arms; emplacements and 

SHELTERS EOR MACHINE GUNS AND 

TRENCH WEAPONS 

41. Depots for Material and Ammu¬ 
nition. —These consist of galleries of 
variable dimensions, opened in the walls 
of the trenches and approaches and usu¬ 
ally lined with timber like mine casings. 
The entrance should be closed with a 
strong door. They are used to store 
water, rations, ammunition, grenades, 
pioneer tools, portable searchlights, field 
glasses, maps, range finders, periscopes, 
lighting pistols, rockets, etc. Depots 
for engineer material are usually in¬ 
stalled in the angles of the approaches. 
Depots for water, rations, tools and 
sand-bags are usually established about 
20 yards to the right of the company 
“command post” (par. 52). Depots for 
arms, ammunition, bombs, grenades, 
and rockets, about 20 yards to the left 
of the same post. An inventory of the 
material should be kept up to date at 
the company “command post.” 

42. Principles of the Employment of 
Machine Guns. 


(1) The personnel and materiel 
should be protected from fire as much 
as possible. 

(2) In order that they may be avail¬ 
able at the moment of attack, it is indis¬ 
pensable that they survive the bombard¬ 
ment. Their protection must therefore 
be specially provided for, by employing 
all of the following means: (a) plac¬ 
ing them under shelter; (b) making 
their emplacements invisible; (c) plac¬ 
ing them in echelon. 

(3) Casemates must be used only 
when they cannot be seen by the enemy, 
such as on the reverse slope, in woods, 
in villages, etc. 

(4) The great importance of making 
the machine guns invisible necessitates 
the construction of firing emplace¬ 
ments outside the shelters, but close 
enough so that the guns can be put in 
action with the least possible delay. 

(5) The firing emplacement may be 
protected by a light roof with very 
slight height, or it may be entirely with¬ 
out overhead protection. The emplace¬ 
ment may consist simply of a pit in the 
open field, situated in front or in rear of 
the parapet and connected with the shel¬ 
ter by an underground passage. The 
machine gun should be placed in action 
at the last moment; it may be simply 
placed on the edge of the pit without 
any protection, or preferably it should 
be covered by a light shield or a low 
parapet joining the natural slope of the 
ground with a gentle slope. The pit 
should be carefully hidden and will usu¬ 
ally not be discovered by the enemy. 
Emplacements of this nature are fre¬ 
quently employed in rear of the first 
lines. 

(6) When the trench is situated on 
the reserve slope, machine guns should 
be emplaced in concealed pits in front 



Field Fortification 


67 


of the trench and connected with it by 
underground passages. 

(7) The requirements of invisibility 
make it necessary to conceal all the ap¬ 
proaches to the firing emplacements by 
making them underground, and to in¬ 
crease the number of emplacements so 
that it will not be necessary to fire daily 
from those to be used in case of an 
attack. 

(8) The emplacement of too many 
machine guns in the first line is danger¬ 
ous; in order to stop an attack they 
should be echeloned to the rear. In fa¬ 
vorable terrain, flank fire should be pro¬ 
vided, to mow down the attacking lines 
as they push forward. Therefore the 
available machine guns should be dis¬ 
tributed between the first line and the 
terrain in rear, with each emplacement 
prepared in a manner suitable to the 
terrain and object in view. 



Fig. 77. —Location of machine-gun 
emplacements. 


43. Machine-gun Emplacements .—An 
emplacement without overhead cover 
may consist of a simple platform con¬ 
structed on the edge of the firing trench, 
where a flanking fire may be obtained; 
or on an approach where the terrain to 
the flank may be covered. The loca¬ 
tions M, Fig. 77, on the first line, and A 
and B , on the approach, will give an ef¬ 


fective flank fire in case of a hostile 
penetrating attack. 

An emplacement with movable light 
head cover and low command is shown 
in Figs. 78, 79 and 80. The emplace¬ 
ment is made in front of the trench, 



Fig. 78.—Plan of machine-gun emplacement 
with movable, light head cover. 


with recesses and benches on each side 
for the personnel and ammunition. The 
head cover is hinged and is made of cor¬ 
rugated sheet iron, covered with earth, 
blending exactly in color and appear¬ 
ance with the front slope of the parapet. 
By raising the head cover with a lever, 
a loophole 3 feet by 1 foot is opened, 
which permits an effective fire. 



Fig. 79.—Profile showing head cover lowered. 

44. Shelters for Machine Guns .—The 
bomb-proof shelters whose details of 
construction have been given constitute 








































08 


Field Fortification 


a series of types from which choice may 
be made, depending upon the tactical 
requirements, the possibilities for defi¬ 
lade, and the materials available. 



Fig. 80.—Profile showing head cover raised, 
machine gun ready to fire. 


a. Shelter with revolving platform 
(Fig. 81).—The platform or support 
for the gun revolves on a circular base. 
The machine gun may be placed in ac¬ 
tion very quickly. The shelter is proof 
against only bullets and shell fragments. 
The roof is made of flagstones in two 
layers with corrugated iron between, 
supported by timber and covered with 
earth. The sides above the ground are 
closed with sand-bags and earth, and 
the emplacement is revetted with planks 
nailed to the posts. 



Fig. 81.—Shelter for machine gun with 
revolving platform. 

b. Shelter of reinforced concrete 
steel rails (Figs. 82 and 83). — This 
gives much greater protection than that 
shown above. The roof is formed of a 
layer of steel rails over a layer of logs, 
supported by timber and firmly bound 
together with wire. Over the rails is a 
layer of earth 1 foot 4 inches thick. 
Protection from direct hits is secured 


by a shield of rails in which a loophole 
is arranged. The walls of the shelter 
should be revetted, and benches should 



Fig. 82.—Profile of machine-gun shelter with 
overhead cover of steel rails. 


be constructed for the personnel and 
ammunition. The roof should be made 
waterproof by covering the rails with 



Fig. 83.—Plan of machine-gun shelter with 
overhead cover of steel rails. 


tar paper. This shelter gives protection 
from shells of small caliber. It has con¬ 
siderable command (4 feet 8 inches) 



Fig. 84.—Machine-gun shelter with roof of 
earth and logs. 
































































Field Fortification 


69 


and therefore should be used only when 
it can be concealed. 

c. Shelter with roof of earth and 
logs (Fig. 84).—This is similar to that 
described above, and has the same plan. 
It is proof against shells up to 6 inches. 
It has considerable command and 



Fig. 85.—Plan of machine-gun shelter with 
roof of steel rails and concrete. 


should therefore be used only where it 
can be concealed. 

d. Shelter with roof of steel rails and 
concrete (Figs. 85 and 86).—The roof 
is constructed of tw r o layers of steel 
rails separated by an 8-inch layer of 
concrete, and covered with earth and 
sacks of concrete, or of cement hard- 



Fig. 86.—Profile of machine-gun shelter with 
roof of steel rails and concrete. 

ened by wetting. When sacks of cement 
are used they should be bonded to¬ 
gether by filling the spaces between 
them with loose cement moistened. This 
shelter is proof against the projectiles 
of large-caliber mortars. 

e. Shelter of reinforced concrete 


(Figs. 87, 88 and 89).—This is used 
when it is necessary to construct a pow¬ 
erful flank defense in the first line and 
it is impossible to conceal it properly. 



Fig. 87.—Location of rein¬ 
forced concrete shelter for 
machine guns. 


It is constructed entirely of reinforced 
concrete. The roof is constructed of 
two layers of steel rails separated by a 
layer of concrete and covered with con- 



Fig. 88.—Plan of reinforced concrete shelter 
for machine guns. 


Crete reinforced with steel rods .3 to .4 
inch in diameter. It will give protec¬ 
tion from hits of the largest projectiles, 
and affords protection for the personnel 



Fig. 89. —Profile of concrete shelter for 
machine guns. 


of two machine guns. The command 
does not exceed 3 feet 4 inches. 

45. Emplacements for Machine Guns 
for Firing at Aircraft (Figs. 90 and 
91).—These emplacements should be 




























































70 


Field Fortification 


constructed in branches of the ap¬ 
proaches or in rear of the front trench. 
Fig. 90 shows a machine gun mounted 
on post with a revolving block; Fig. 91, 
on a wheel with its axle fixed in a barrel 
filled with sand. 


i 



Fig. 90. —Emplacement for a 
machine gun mounted on a post 
for firing at aircraft. 


46. Emplacements and Shelters for 
Trench Weapons. —In trench warfare, 
batteries of light mortars of the first 
line are generally situated between the 
front and the support trenches. Like 
machine-gun emplacements they are of 



Fig. 91.—Emplacement for a machine 
gun mounted on a wheel. 


two types, viz., with and without over 
head cover. Whenever overhead cover 
is used, if practicable, alternative em¬ 
placements without it should be con¬ 
structed nearby. The emplacements 
should be concealed as much as possi¬ 
ble, and for this purpose the command 
should not be greater than that of the 
adjacent trench. The guns should be 
echeloned as indicated for machine 
guns. 

47. Emplacements for Trench Mor¬ 
tars, zvithout Overhead Cover. —Fig. 92 
is a plan of an emplacement for two 
trench mortars. A battery of four to 


six mortars should be divided up into 
platoons of two mortars, by traverses. 
A lateral trench (Fig. 93) affords com¬ 
munication between the platoons and 
for the ammunition service; this trench 
branches off from the system of ap¬ 
proaches. The mortars are placed on 
platforms 3 feet 8 inches square (Fig. 


r 



Fig. 92. —Plan of an emplacement for two 
trench mortars. 


95), separated by traverses made of 
sand-bags or gabions 3 feet 4 inches 
thick to localize the effects of projectiles. 
Niches are constructed to one side of 
each platform to enable the gunners to 
fire the mortars under cover. Ammuni¬ 
tion recesses (Fig. 94) are constructed 




Fig. 93.—Section C-D, Fig. 94.—Section A-B, 
Ammunition recess, communicating trench.' 

near the mortar platforms to shelter a 
first reserve of supply. A protected ob¬ 
servation post should be constructed be¬ 
tween the platoons and in rear for the 
battery commander, in accordance with 
the principles given in Part IV. 









Field Fortification 


71 


48. Emplacements with Overhead 
Cover (Fig. 96).—The roofs should be 
constructed as for shelters for light field 



Fig. 95.—Section E-F, mortar platform. 


fortifications. The type shown is formed 
of two layers of logs separated by a 
foot of earth and covered with sand¬ 
bags and earth. 

49. Communication. —A battery of 
light mortars is, like a machine-gun bat- 



at the angles in the approaches (Fig. 
97). 

For equipment, drinking water, ra¬ 
tions, lanterns lighting sign-posts, etc., 
niches of various sizes are constructed 
in the parapet; or recesses, lined with 
timber, are constructed in the walls of 
the trenches and approaches. 



Fig. 97.—Location of command 
posts, telephone stations, kitchens, 
etc. 


Fig. 96.—Emplacement for trench mortars 
with overhead cover. 

tery, essentially a mobile unit, and 
should be constantly in communication 
with the infantry unit to which it is 
attached. 

Part VI 

IMPROVING LIVING CONDITIONS IN THE 
TRENCHES 

50. General Principles. —Order and 
sanitary conditions must be rigidly ex¬ 
acted in the trenches, or they would 
soon become untenable or very un¬ 
healthy. 

Command posts, telephone stations, 
first-aid stations, trench depots, kitch¬ 
ens, the supply of drinking water, la¬ 
trines, and lavatories should generally 
be constructed in short, covered trenches 


51. Command Posts (Figs. 98 and 
99).— Besides their combat posts in the 
firing trench, the various commanders 
should be provided with shelters called 
“command posts.” Their size and ar¬ 
rangements will depend upon the grade 
of the commander who occupies them. 
They should be large enough to accom¬ 
modate the commander and his assist¬ 
ants or staff who must be constantly 
with him. They must be located so that 
they can easily be found, even by order¬ 
lies of another command; the routes to 
them must be plainly marked, and their 
position shown by flags and colored lan¬ 
terns if this can be done without being 
visible to the enemy. 

Figures 98 and 99 show a company 
command post. The captain has a room 
8 by 10 feet, and his lieutenants a room 


















72 


Field Fortification 


10 by 13 feet. A telephone and some 
tools are placed in the lieutenants’ room. 
The furniture consists of cots, benches, 
stools, and a table. Ventilation is secured 
by two pipes which run at an inclination 
to the surface of the ground, or by ver¬ 
tical holes over the wall of the shelter. 
The shelter is heated with a stove or 
fireplace in a recess in the captain’s 
room. The stove pipe should run the 
entire length of the shelter so as to 
utilize all the heat. 

The company command posts must 
have on each flank: 

a. 20 yards to the right, a depot of 
rations, tools and sand-bags. 

b. 20 yards to the left, a waterproof 
shelter for arms, ammunition, grenades, 
rockets, etc. 

They should be plainly marked C. P. 
No. —. All material should be always 
collected and inventoried in these fixed 
and known points, and nowhere else. 
In each command post there should be 
a bulletin board of uniform model to 
record orders, and materiel. 



Fig. 98.—Plan of a company command post. 


52. First-aid Stations .—These are 
connected with the fire trench by a com¬ 
municating trench wide enough to carry 
a litter. They are constructed like other 
shelters. The walls are covered with 
straw mats or hurdle work, which must 
be changed frequently. They should be 


at least 8 by 12 feet in size. Two cots 
should be placed against one wall, and a 
bench for the wounded to sit on against 
the other. 



Fig. 99.—Company command post, section 
A-B. 


53. Kitchens .—These should be con¬ 
structed in shelters. The stove pipes 
should project somewhat above the top 
of the shelter to secure good draft. In 
addition, numerous ventilating holes 
must be made. They may be made 
large enough to accommodate the roll¬ 
ing kitchens. Small fires built of dry 
wood in the bottom of deep trenches do 
not betray the trenches. 

54. Latrines .—It is absolutely neces¬ 
sary to construct latrines near the 
trenches and approaches. They may be 
without overhead cover as in Fig. 100, 
or with it as in Fig. 101. It is necessary 
to provide comfort and security. When 
practicable the place should be revetted 
with timber, and supports constructed. 
Cleanliness should be insisted upon, the 
deposits covered with earth daily, and 
the location changed when the pit is 
three-quarters full. The entrance trench 
should be paved with stones for at least 
10 yards. The latrines should be ar- 

























































Field Fortification 


73 


ranged on the arc of a circle, five or 
six radiating from a central point, or in 
the form of a cross, or on both sides of 



Fig. 100. —Latrine without 
overhead cover. 


a special trench. The nearest latrines 
must be at least 30 yards from the prin¬ 
cipal approaches. 

55. Lavatories. —These are impro¬ 
vised of tin or wood so as to form a 



Fig. 101. —Latrine with overhead 
cover. 


number of basins in a row, with holes 
in the bottom, placed above a wooden 
trough which receives and carries off 
the water to a cask or drainage pit. 
There should be a grating for the men 
to stand on. They should be constructed 
in a branch trench, covered if practica¬ 


ble. The floor of the trench should have 
a decided slope. 

56. Shower Baths .—These should be 
installed in a deep shelter or in a cave 
shelter. A simple arrangement is to 
provide one or two kettles for heating 
water, tubs or casks for storing water, 
placed about 9 feet above the ceiling of 
the shelter. The tubs or casks should 
be connected with a pipe fitted with 
sprinklers, properly spaced. There 
should be a grating on the floor, and the 
bottom of the approach should have a 
fairly steep slope towards a drainage pit. 

57. IVater Supply .—This usually con¬ 
sists of several large casks filled with 
pipes if practicable, otherwise the water 
is carried to them. There should be an 
interval of at least ten paces between 
casks to avoid crowding and mud 
puddles. 


conclusion 

58. The numerous works described 
herein would seem at first glance too 
complicated and massive to be ever con¬ 
structed in actual warfare, but they are 
the results of actual experience in mod¬ 
ern trench warfare, and numerous ex¬ 
amples of them exist on the western 
front today. By means of work of this 
character the Germans have been able 
to hold the conquered portions of France 
with the minimum of men. Their bomb¬ 
proof shelters and the arrangements for 
the comfort and health of their men 
have especially occupied the thought of 
their highest commanders and engineers. 

In many stances their captured under¬ 
ground works have been found intact in 
spite of bombardments by the heaviest 
artillery. Some of these shelters have 
been excavated to a depth greater than 
40 feet, with galleries 150 yards long 
























74 


Field Fortification 


and 7 feet high, completely lined with 
timber. On both sides of these galleries 
are large rooms, lined with timber, well 
ventilated by oblique shafts, and fur¬ 
nished with field cots with wire springs. 

The timbering was so strong that in 
one case a 12-inch projectile which fell 
exactly over the top of the entrance did 
no damage except to crack a post. The 


exits are very numerous, and consist of 
six or seven stairways furnished with 
steel treads to avoid slipping, and sev¬ 
eral ramps with gentle slopes to permit 
of rapid exit in case of alarm. The shel¬ 
ters were heated with excellent stoves 
jand lighted with electricity; the light 
and telephone wires ran along the walls, 
supported by glass insulators. 





CHAPTER V 


ORGANIZATION OF INTRENCHED ZONES 

• 1. General Principles, Definitions. 
The organization of an intrenched zone 
comprises the establishment of elements 
of frontal fire and of flank fire, sweep¬ 
ing effectively the terrain. 

These elements of fire take advan¬ 
tage of the natural accidents of the ter¬ 
rain : woods, houses, inhabited places. 

The elements of fire are occupied by 
fixed garrisons designated by the com¬ 
mander whose strength varies with cir¬ 
cumstances. 

The group unit is generally the pla¬ 
toon, at the minimum a section. 

Successive lines of elements of fire 
are established in rear of the first line, 
so that they may come into service as 
soon as the first line falls. 

Hence elements of fire must be estab¬ 
lished in breadth and depth. 

2. Organization in Width—Strong 
Points. —Group of elements of fire, so 
arranged that by their reciprocal sup¬ 
port they will permit the defender to 
stop the assailant. The strong point is 
surrounded by a continuous obstacle, 
and may contain a redoubt. 

It is always occupied by a consti¬ 
tuted unit, commanded by its chief, who 
is held responsible for the constant re¬ 
pair and improvement of the defensive 
works, and of the defense of the place 
to a finish. The strength of this unit 
will depend on the importance of the 
strong points; it will generally be a 
company or a fraction of a company. 

The strong points will be distributed 
along the front (width) according to 


the importance of the portions of ter¬ 
rain to be held and the facilities of as¬ 
suring flanking dispositions. 

3. Organization in Depth. — Fire 
power alone will not be always suffi- 

• cient to assure the defense of a posi¬ 
tion ; the defensive system must be or¬ 
ganized so as to provide for immediate 
counter attacks, intended to retake all 
or a part of the last position. To this 
end, it is necessary to have: 

(1) In rear of the first line of strong 
points, other strong points intended to 
limit any success of the enemy. 

(2) Troops in reserve intended for 
counter attacking. 

4. Organization in Width and Depth 
—Supporting Points. — The strong 
points are therefore grouped in width 
and depth. These groups take the name 
of supporting points. Their defense will 
be entrusted to a fraction (battalion or 
group of companies) placed under one 
commander, who will furnish the gar¬ 
rison of the different strong points and 
the reserve troops. Artillery may be 
allotted to certain supporting points. 

The supporting point is surrounded 
and partitioned by systems of barb 
wire; it always has a redoubt, made up 
of one or two strong points. 

The necessity of establishing as many 
as possible continuous lines of trenches 
has been demonstrated by the war and 
consecrated by the Battle of Verdun. 
The isolated strong points, separated 
by uncovered or almost uncovered in¬ 
tervals, are easily located by aerial 
photography and become, during the 


75 


70 


Field Fortification 


preparation of an attack, the favorite 
targets for artillery. Moreover, the ab¬ 
sence of continuous lines prevents the 
rapid occupation of the intervals by the 
defenders and permits the enemy to 
filter in between the strong points. 

The continuous line does not suppress 
the strong point, but the latter must be 
sunk in a network of trenches, zigzags 
and false or dummy trenches. 

5. Sector .—The union of several sup¬ 
porting points under the same command 
forms a sector. Each sector disposes 
always of its own reserves distinct from 
those of the supporting points. It has 
generally some artillery. 

6. First, Second, Third Positions .— 
The first position of a defensive or¬ 
ganization then consists of a line of sup¬ 
porting points. In war a second position 
will always be organized, and, when 
necessary, a third, constructed as the 
others. The distance between these 
positions must not be less than from 1 
to 2 kilometers. It may even be greater 
when circumstances demand. 

Each position comprises several lines 
united by numerous zigzags and parti¬ 
tioned by wire entanglement. Arrange 
in the entanglements of the second and 
third lines passages which will allow 
movement of the reserves (reinforce¬ 
ment, counter-attack). 

Part I 

trace: or the firing line 

7. The first thought must be given to 
creating a powerful front by installing 
a solid fire line. Its trace, resulting 
from the emplacement and orientation 
of each element, must satisfy success¬ 
ively the following conditions: 

(1) Organization of flanking dis¬ 
positions. 


(2) Installation of accessory de¬ 
fenses. 

(3) Simultaneously: (a) Rectifica¬ 
tion of the trace of the position; ( b ) 
search for and installation of observa¬ 
tions; (c) construction of trenches; 
(d) clearing up and range finding of 
the field of fire. 

(4) Construction of communications. 

(5) Construction of shelters and in¬ 
cessant reinforcement of trenches, shel¬ 
ters and observatories. 

8. Organization of Flanking Disposi¬ 
tions .—A firing line is defended better 
by flank fire than by direct fire. 

The near flanking dispositions must 
be carefully and methodically studied, 
as soon as a position is chosen. These 
flanking dispositions are organized in 
such a way: 

(1) That they cannot possibly fire 
into their own line. 

(2) That they are as much as possi¬ 
ble sheltered from frontal sight and 
fire of the enemy. 

9. The Machine Gun Is the Flanking 
Arm .—The majority of the machine 
guns with their personnel are placed in 
shelters, in very deep saps. At the end 
of the bombardment the men bring out 
the piece and set it up on the emplace¬ 
ment, if it still exists, or along the 
trerch parapet, unprotected. 

Examples of flanking dispositions 
suitable to each element: (a) In the 
first place, the trenches are broken in 
trace so as to adapt them as much as 
possible to the terrain, while flanking 
each other mutually. 

Fig. 1 gives a scheme of ensemble 
of a broken trace. 

A careful examination of the figure 
indicates very clearly the ensemble of 
the flanking dispositions. 



Field Fortification 


77 



Fig. 1.—Scheme of ensemble of 
broken trace. 

Fig. 2 gives some details of organiza¬ 
tion of the flanking arrangements. The 
machine guns M and M' are sheltered 
from direct view and fire by epaule- 
ments. The normal wire entanglement 
is interrupted in their sector of fire, and 
a low entanglement is installed there, 
which will not be cut down by their fire. 



Fig. 2.—Flanking arrangements (details). 


( b ) Small salients (Fig. 3) are fre¬ 
quently and advantageously employed. 

This “forward traverse” (Fig. 3) 
must be, at least, 6 meters in thickness 
at the base (along the trench), 4 meters 
at the top. The lateral branches are 4 
meters long. The branches forming a 
redan are each 2 meters long. There 
can then be made a passage in rear to 
facilitate movement. The fife trench 
of the salient must be very narrow (2 
feet 8 inches). 



Fig. 3.—Small salient or 
forward traverse. 

(c) From the position, short stand¬ 


ing trenches are carefully constructed, 
sheltered by a strong parados against 
the fire of the neighboring elements of 
the general fire trench. 

Flanking detachments are installed 
in these trench elements (Fig. 4). 



Fig. 4.—Element of forward trench. 

( d ) The terrain may require the es¬ 
tablishment of special advanced organi¬ 
zations. These positions are occupied 
by groups of firers. 

An approach trench connects the ar¬ 
rangement with the first line trench 
(Fig. 5). 



Fig. 5.—Special advanced organized position. 

( e ) It may be necessary to push a 
special trench element forward, so as to 
sweep a ravine, a valley, or a depression 
of the ground which cannot be seen 
from the first line. The approach 



Fig. 6.—Element of forward trench. 

trench of this position will serve for 
flanking a part of the principal front 
(Fig. 6). 

(/) Finally, in woods, it will be log¬ 
ical to adopt the tenaille trace (Fig. 7). 




-Vi 




Fig. 7.—Tenaille trace in woods. 













78 


Field Fortification 


The positions will be selected so as 
to be invisible through the woods and 
from aircraft above. 

( g ) From center to center the flank 
fire is assured by the installation of 
flanking detachments in effective em¬ 
placements. The flanks of each trench 
should not be covered by any other. 
Each should be solidly supported on its 
flanks so as to avoid enfilade fire and 
being turned. 

Establish liaison by rifle fire and com¬ 
munications by defensive approach 
trenches, with neighboring organiza¬ 
tions to right and left. 

( h ) Finally, so far as the artillery is 
concerned, the batteries from the be¬ 
ginning must be placed relatively far 
forward; it is only from advanced posi¬ 
tions that artillery can possibly give a 
flanking fire for neighboring sectors. 

( i ) If in the night installation of po¬ 
sitions the broken trace lines cannot be 
obtained, flank fire may be obtained, 
after building the trenches, by sapping 
outstanding trenches. However, take 
care that the enemy may not be able to 
enfilade them. 

10. Construction of Accessory De¬ 
fenses. —Infantry, of good morale, can 
repulse all attacks if it has a good field 
of fire of 50 meters in depth and if the 
progress of the enemy is retarded by 
accessory defenses. 


(Noth. —The construction, installa¬ 
tion and destruction of accessory 
defenses are the objects of special 
lessons.) 

Commence by putting down the en¬ 
tanglement the farthest away so as to 
prevent the use of flame projectors. 
Use the counter slope a great deal, the 
low places, woods. 

11. Simultaneously —(a) rectifica¬ 
tion of the trace of the position. —Un¬ 
der the protection of the fire of the first 
line which has dug in when it was 
forced to stop, the emplacement of the 
position is chosen in such - a manner 
that the firing trenches are hidden from 
view as much as possible and conse¬ 
quently unexposed to artillery fire. The 
emplacement should be such that sup¬ 
plies and reinforcements can come up 
under cover. 

The different solutions which take 
into account at the same time the field 
of fire and cover, present each advan¬ 
tages and inconveniences. 

Take two crests IF of considerable 
relief, separated by a valley V (Fig. 8). 

(1) Position at the foot of the slope 
at B .—Good field for sweeping fire, 
emplacement hidden from artillery Al, 
but dominated by the enemy at K; 
moreover, the movements of reinforce¬ 
ments from the crest will be difficult. 

(2) Position at C, on the military 



Fig. 8.—Emplacement of defensive positions. 



Field Fortification 


79 


crest. —Good commanding position. 
Good fire effect, sweeping on CB, 
plunging on BPK. 

But' the hostile artillery will regulate 
easily its fire on C; the movements on 
DC will be difficult; the trenches in¬ 
clined on the slope will be very vulner¬ 
able, solution sometimes imposed by 
reason of the long views. It is always 
indicated for advanced combat posts. 
The installation of a line of surveillance 
or of machine guns could come from 
behind the crest by saps pushed under 
the crest. 

(3) Position at D on the real or to¬ 
pographical crest. —Good views on dis¬ 
tant debouching points NKB. Easy to 
hide if care is taken to place the 
trenches at 30 or 40 meters in front of 
the crest to avoid outlining the parapet 
against the sky. 

Movements to the rear easy and hid¬ 
den from sight. Very easy solution in 
moderately undulating ground. In 
rough country, the slope CD being very 
steep and short, the topographical crest 
presents the same difficulties as the 
military crest. 

(4) Position at B, on counter slope. 
—Possesses a very short field of fire, 
is dominated by the terrain in front, but 
offers a considerable advantage; it is 
completely sheltered from view and 
from infantry fire. Hard to locate, and 
so little exposed to artillery fire. 

The friendly artillery on the contrary 
can lend, by barrage fire on the crest, 
considerable and accurate support to 
the intrenched infantry; on the other 
hand, the enemy debouching from the 
crest, received by the fusillade and 
stopped by the wires, hidden from 
sight by the counter slope, undergoes a 
considerable effect of surprise, which 


is all the more demoralizing for that 
reason. 

These trenches on the counter slope 
lend themselves admirably to close com¬ 
bat. Occupied by defenders of solid 
morale, protected by thick accessory de¬ 
fenses, they permit of stubborn and 
long drawn out resistance, even when 
held by weak effectives. The counter 
attack, launched at the moment when 
the enemy, surprised, stops, hesitating, 
against the entanglement, will have 
sure results. With this arrangement, a 
line of surveillance must necessarily 
be placed at C. Machine guns placed 
on this line, and capable of circulating 
on cover between C and B, will produce 
very powerful and deadly effect. 

The advantages of organized posi¬ 
tions on counter slopes have been con¬ 
secrated by the war and particularly 
by the defense of the advanced posi¬ 
tions before Verdun. Their advan¬ 
tages may be summed up by quoting 
Col. Piaron de Montdesir: 

Formerly, with arms of short life, 
and slow loading, it was necessary to 
have a range long enough to permit re¬ 
loading. This reason no longer exists. 
Modern arms have a long range and 
load quickly, several shots being intro¬ 
duced at a time, thanks to the magazine. 
Long range fire may be utilized by the 
advanced combat posts and caponier 
trenches. It suffices to utilize rapidity 
of fire to obtain by the factor time 
what used to be obtained by the factor 
distance. Moreover, the effects of fire 
at short range are much more sure. 
The fire would not be good if the rifle¬ 
men were subjected to the neutralizing 
fire of artillery, but, having escaped 
this, and only receiving a fire which 
they oppose by their own, their cover 
gives them a marked advantage. (Col. 
Piaron de Montdesir: “Essay on the 
tactical employment of field fortifi- 
cations. ,, ) 



80 


Field Fortification 


(a) Choice of emplacement. —The 
importance of a free and extended field 
of fire is secondary to that of the infan¬ 
try, being sooner in its combat posi¬ 
tion; a position, excellent for intrench- 
ment, may have a limited field of fire. 
If the frontal accessory defenses are 
solid, a field of fire of from 200 to 50 
yards and even less (30 yards in Ar- 
gonne) is sufficient. A commanding 
position, chosen so as to obtain an ex¬ 
tended field of fire—for example on 
the slopes of a line of heights facing 
the enemy—is generally to be avoided. 

It is of the greatest importance that 
the fire trenches should be hidden from 
sight as much as possible, and, conse¬ 
quently, exposed as little as possible to 
artillery fire. Access should be possi¬ 
ble under cover. Therefore it is recom¬ 
mended, in open country, instead of 
placing fire trenches forward of the 
crest, to place them somewhat in rear 
of the crest. 

The infantry, then, in the choice of 
its positions, is considerably more inde¬ 
pendent than formerly. Only, it abso¬ 
lutely must seize the parts of the ter¬ 
rain which serve for the observation by 
the friendly artillery. 

( b ) Search for observatories .—The 
search for emplacements 'which give 
good views over the hostile position is 
of the highest importance. Flank 
views are particularly interesting. Ob¬ 
servatories provided with means of op¬ 
tical and telephonic communication will 
be installed in trees, ruins of houses, 
straw stacks, and on all elevated points 
giving wide views. 

If there are, forward of the position, 
points which permit the enemy ob¬ 
servers to see into the friendly posi¬ 
tion and in rear of it, an effort must be 
made to find out whether, from the ad¬ 


vanced positions, these points can be 
taken under an effective fire. The pos¬ 
session of cover in advanced terrains, 
such as houses, mills, which protect the 
hostile artillery observers, must be dis¬ 
puted desperately. 

(c) Construction of trenches. —The 
trenches along the trace staked out are 
constructed according to the principles 
explained in a former lecture. The 
workers are hidden from distant sight 
by a parapet mask made of branches 
and brush. The work is done simul¬ 
taneously with the range finding and 
the clearing up of the field of fire. 

(d) Clearing up and range finding 
of field of fire. —The clearing up con¬ 
sists in removing or levelling crops, 
brush, small walls, houses even, to fa¬ 
cilitate direct and flank fire. 

A field of fire is range-found when 
fire can be opened with the exact sight 
setting, or visible objects in it. Employ, 
for range finding, observation by avion, 
reconnaissance by range finding parties. 
Use carefully and rapidly the informa¬ 
tion obtained. In woods, remove to the 
height of a man the bark of the trees 
in the field of fire on the side toward 
the friendly position. Whitewash this 
face. In this way, at night, the visibil¬ 
ity of attacks or hostile patrols is 
augmented. 

12. Construction of Communications. 
—Every defensively organized position 
must be provided with organs of com¬ 
munication, which will allow the rapid 
upbringing of supplies and reinforce¬ 
ment which, covered from distant view, 
is effected either by following defiladed 
routes, or by the way of the approaches, 
where trace, construction and arrange¬ 
ment have previously been treated. The 
number of these approaches will be de- 



Field Fortification 


81 


termined in Part IV of the present 
lecture. 

13. Creation of Shelters and Rein¬ 
forcement of Works. — Create, for 
troops of the line of fire, combat shel¬ 
ters on this line, and for the available 
troops and the reinforcements deep 
solid shelters in deep saps, with defi¬ 
laded communication towards the rear. 

Part II 

ELEMENT OF PLATOON OR SECTION 

TRENCH AND GROUP OF ELEMENTS OF 

trench 

14. Groups of trenches are generally 
constructed for one company. They 
are composed of platoon trenches, or 
section trenches, whose intervals are 
connected by observation approach 
trenches with fire crests (defensive 
approaches). 

The group of several elements of pla¬ 
toon or section trench will constitute a 
company group. 

15. Platoon or Section Trench. —It 
will be built generally, and exception 
made of flanking dispositions already 
indicated, in the form of a flattened 
lunette, having approximately 50 me¬ 
ters of trench available for fire. (Fig. 
9.) 



Fig. 9.—Element of platoon trench. 


Distance between traverses, 6 to 9 
meters, which may in exposed places 
be reduced to 4 or 5 meters, 2 to 4 
meters thick at the top. The total 


length of the front of the trench, with 
5 traverses in front (every 6 meters) 
and one traverse on each flank, will be 
about 70 meters. 

The length of the excavation will be 
from 85 to 90 meters. 

The face, or front, properly speak¬ 
ing, with its five traverses, will have a 
total front of about 45 meters (32 me¬ 
ters of fire crest). Each flank will 
have from 10 to 12 meters of develop¬ 
ment, including a traverse of 3 meters. 

Do not place traverses at the salients. 
Stake out the traverses adjoining a sa¬ 
lient at from 3 to 5 meters from it. 

The section trench will have the half 
of the development of the platoon 
trench, but will comprise the same 
elements. 

16. Group of Trenches for a Com¬ 
pany. —The platoon trenches will com¬ 
municate (Fig. 10 ) : 

(a) Between themselves: by means 
of the approach trenches of surveil¬ 
lance, prepared as a defensive approach. 

( b ) With the rear and the command 
post of the captain, by the approaches. 

The trenches of the different com¬ 
panies communicate with each other at 
first only by the rear, then lateral com¬ 
munications are established, and these 
are prepared as defensive approaches. 
A continuous line of trench is thus es¬ 
tablished along the whole front. 

The development of the 4 platoons 
may occur when the battalion reserve, 
situated 200 or 300 meters in rear, may 
make its action felt rapidly; if not, the 
company field work comprises but three 
trenches in the first line. 

17. Group of Trenches for a Bat¬ 
talion. (Fig. 11 .) 

18. Group of Trenches for a Regi¬ 
ment. (Fig. 12 .) 






8 2 


Field Fortification 


19. Group of Trenches for a Brigade. 
(Fig. 13.) 

Part III 

PLAN FOR The: ORGANIZATION OF A 
SUPPORTING POINT 

20. The organization of a supporting 
point is, in each particular case, a prob¬ 
lem whose data may, and whose solu¬ 
tion will, depend on the military situa¬ 
tion, the terrain, the time, the workers 
and material available, etc. No precise 
rules of organization can be given, but 
only guiding principles. These prin¬ 
ciples are outlined in the figures repre¬ 


senting the organization of works for a 
company, a battalion, a regiment, and 
a brigade. (Figs. 10 to 13.) 

The organization comprises the es¬ 
tablishment of successive lines of de¬ 
fense, the permanent installation in 
these lines of fractions intended to as¬ 
sure its defense, or to constitute coun¬ 
ter-attack troops; it comprises finally 
the largest use of approaches, shelters, 
wire entanglement, platforms and shel¬ 
ters for machine guns and trench 
weapons, so as to limit the enemy’s ad¬ 
vance and to retake, by counter attack, 
the ground lost. 









Field Fortification 


83 


21. Successive Lines of Defense .— 
The successive lines of trench bear the 
following names: 

(1) Firing trenches. 

(2) Support trenches. 

(3) Intermediary trenches. 

(4) Reserve trenches. 

22. Firing Trench .—It is the em¬ 
placement where the advanced frac¬ 
tions receive the first shock. They per¬ 
mit the garrison to utilize, to a maxi¬ 
mum, its force of resistance and 
to weaken the enemy considerably 


so as to prepare the counter attack. 

They are sometimes double. This 
method permits an immediate counter 
attack, and in case of intense bombard¬ 
ment, a rapid retreat of the garrison, 
which, however, is held near. This 
trench is called the cover. It is 
generally at about 40 meters from the 
first line. 

The firing trenches, covered by a 
large zone of accessory defenses, must 
be preceded by advanced post trenches, 
or at least rifleman’s pits, likewise pro- 



Firing trenc/ies Pummy Trench 

==*== Appregch S,(e/rmwici>h/r]X0ich tV,re Pn toe foment 

-.with I Crest |<n> TajMfe/ir6t//rterAfah 

—^ * £CC S F— M,c/,we</»n 


Fig. 11.— Group of trenches for a battalion. 















84 


Field Fortification 


tected by accessory defenses. These 
intrenchments permit: 

( a ) To watch over the accessory de¬ 
fenses, and to hold at a distance the 
observers and the hostile sharpshooters. 

( b ) To prepare, by assuring the ad¬ 
vanced surveillance of the terrain, the 
task of the patrols and sudden enter¬ 
prises, which assure the mastery of the 
terrain. 


(c) In case of attack, to oppose to 
the enemy a first resistance. They as¬ 
sure thus the opening up of the flank 
fire, and they give the commanding offi¬ 
cers the necessary time to prepare and 
spring the counter attack before the 
first line is reached. 

23. Support Trenches .—The line of 
the support trenches will be established 
at from 100 to 200 meters in rear of the 


/ /VC.U “ ( 1000 “*• Hit') 





















1 1 f /f00 


Field Fortificati on 


85 


u:.. 

I 


##•( 



I 



Fig. 13.—Group of trendies for a brigade. 


































Field Fortification 


80 


trenches of the first line, and should 
hold them under its fire. They permit, 
in case of the yielding of the first line, 
to limit the recoil. Their defense gives 
the available troops of the sector time 
to counter attack. They must hold the 
first line trenches under their fire. Each 
one is preceded by a wire entanglement. 
In case of attacking, they play the role 
of parallels in rear of the first line for 
the third and fourth waves of attack. 

24. Intermediary Trenches .—One or 
two intermediary lines will be organ¬ 
ized in rear, likewise at 150 or 200 me¬ 
ters one from the other, sweeping as 
much as possible the trenches in front 
and the communications which connect 
them; they will be developed according 
to the terrain. They permit: 

Sheltering momentarily the available 
elements of the sector; 

Limiting the zone in which an enter¬ 
ing enemy could spread out. 

All the trenches, whether advanced, 
of the first line or of the second line, 
are provided with look-outs, whose mis¬ 
sion it is to alarm their comrades, to 
start the barrage or to repeat the sig¬ 
nals of the first line. 

25. Reserve Trench. — Finally, in 
rear of the supporting point (400 to 
1,000 meters), a solid redoubt, com¬ 
pletely closed. If the terrain demands 
it, it can be divided into two distinct 
works, both closed. The role of the re¬ 
doubt is to offer to the enemy a last 


resistance, pushed to the limit, to inter¬ 
fere with his movement and his estab¬ 
lishing himself on the terrain which he 
has won, and to favor the counter at¬ 
tacks made by the sector reserves. The 
redoubt is formed either by a natural 
position or by an artificial construction. 1 

The emplacement of the redoubts is, 
as much as possible and as closely as 
possible, defiladed from distant view, 
and hidden from aerial observation; it 
contains well-constructed accessory de¬ 
fenses, shelters for the reserves of the 
center of resistance, considerable sup¬ 
plies (5 days at least) of food and 
ammunition, as well as the command 
post of the commanding officer of the 
center of resistance. 

The custody of the redoubt will be 
entrusted to an energetic chief, who 
will fight to a finish. 

26. Communications .—A system of 
communications, easy and well-defiladed 
routes, will facilitate the life and de¬ 
fense of the center of resistance. The 
different echelons of trenches are con¬ 
nected with each other by very deep 
and narrow trenches, arranged for ob¬ 
servation and defense foot by foot. 
Avoid long, straight elements, and put 
in many traverses. 

The communications are covered by 
accessory defenses, placed in the imme¬ 
diate proximity of the trenches so as 
to obstruct them immediately (chevaux 
de frise, sandbags, etc.). Along the 


1 In the offensive in Champagne in September, 1915, the French found themselves stopped 
by redoubts organized under ground, having the form of a star and which were called for 
that reason star redoubts. 

At about 10 meters below the ground is a cave shelter of vast dimensions, in which is 
lodged a company and are stored machine guns, trench weapons and several days’ rations. 
Five or six trenches executed by a very deep sap, without any relief, or by a mine gallery, 
radiate in all directions and come out at the surface of the ground. The exits form half a 
dozen points on the imaginary circle of a radius of 100 meters. 

In each trench or gallery a ralroad permits the rapid movement of weapons and 
ammunition. 

At the exit, holes with parapet effaced, for trench weapons and machine guns, with 
emplacements carefully chosen so as to sweep the exits. 

Moreover, these redoubts are mined and can be blown up from any one of the exits. 




Field Fortification 


87 


route, branches are constructed, where 
platforms, shelters for machine guns 
and trench weapons are installed. Ac¬ 
cording to the position of these com¬ 
munications, whether on the axis or on 
the flanks of the supporting point, they 
are prepared with single or double fire 
crest. 

Number .—Between the fire trench 
and the last support trench there must 
be at least one approach per element of 
platoon or section trench. 

In rear of the last support trench and 
for every 300 meters of front, two ap¬ 
proaches, at least, for the forward 
movement; a third approach for evacu¬ 
ations and the movements towards the 
rear (evacuation approach). This ap¬ 
proach must have a trace and profile 
which permit the easy passage of the lit¬ 
ters. It is on the route of this third 
approach that the protected first-aid 
stations will be branched. 

The approaches in rear of the sup¬ 
porting point must be pushed to 4 or 5 
kilometers, according to the terrain. 
They must permit the circulation of 2 
men abreast, but they will then be deep¬ 
ened (2 meters at least) and carefully 
constructed at the angles, so as to assure 
sufficient protection. Recesses with exit 
steps will be arranged every 100 meters 
so as to facilitate circulation, and in 
case of need, a rapid exit. 

The approaches will be connected, as 
closely as possible, to the command 
posts and observatories. 

27. Shelters .—The shelters will be 
sufficiently numerous to shelter during 
bombardment the whole of the occu¬ 
pants of the supporting point, with the 
exception of the observers and the in¬ 
dispensable look-outs, themselves placed 
in each line of defense under defiladed 
and protected observatories. 


The commanding officer must see to 
it that these shelters are unceasingly 
improved so that they can resist projec¬ 
tiles of 210 mm. and their living condi¬ 
tions become better. 

28. Assembly Point—Preparation of 
counter attacks .—The preparation of 
counter attacks will be studied with 
care, under the most probable hy¬ 
potheses ; their success will depend 
upon their suddenness and violence. 

Special shelter of assembly points 
will be established for the partial re¬ 
serves of each strong point and for the 
reserve of the supporting point, in em¬ 
placements chosen so as to act rapidly 
towards the menaced points. 

Communications issuing from these 
shelters will connect them to the gen¬ 
eral system of communications. More¬ 
over, communications or special exits 
will be created for counter attacks 
(ramps, steps, facing the enemy). In 
particular, oblique passages well enfi¬ 
laded by the trenches in rear will be 
opened in the accessory defenses. 


-1 

... 

JBL, 

"h \ 

i 1—| 

t - 3 

ii.eo *1 




Fig. 14.—Four assembly 
points for section. 


The arrangement to be given to the 
assembly points will be essentially vari¬ 
able. While providing for the troops 
the best shelter possible (in general 2 
meters in depth and 1 in width), meas¬ 
ures must be taken to provide them an 
easy way of debouching (Figs. 14 and 
15). 

In the preparation of a terrain, in 














88 


Field Fortification 



Fig. 15.—Assembly point for 
platoon. 


view of an attack, the troops designated 
for the attack will wait for the instruc¬ 
tions of the chief concerning the 
preparation of the assembly points. 

29. Command Posts. —Strong and 
supporting points have each a com¬ 
mand post connected electrically with 
the front (trenches), with the rear 
(higher command and the artillery), 
with the neighboring strong points, and 
with the command post of the support¬ 
ing point. 

Each office of command of a sup¬ 
porting point must be connected with 
the neighboring supporting point, and 
with the commanding officer of the 
section. 

The command posts must be easily 
found, even by liaison agents of other 
units. Mark out clearly the itineraries, 
mark the emplacements, for example, 
by day, with flags, by night with col¬ 
ored lanterns, or any other special sign, 
visible from the approaches, but defi¬ 
laded from the enemy’s view (small 
niches). 

30. Telephone Connections. — They 
are of two kinds: 

(1) Communications for the officer 
of command established by the tele¬ 
graph sappers. 

(2) Interior communications between 
units of infantry and artillery or con¬ 
nection infantry and artillery, estab¬ 


lished by the regimental telephonists. 
Fig 16 gives an example of the 
logical organization of a sector, held by 
a regiment of three battalions, having 
each three companies in the first line. 
The regiment must, as a rule, connect 
up with the brigade and with the 
groups of light artillery which operate 
on its front. The brigade post is in 
general organized by units of telegraph 
sappers. 

31. Trench Weapons. — Numerous 
trench weapons (trench cannon, spe¬ 
cial mortars, lance bombs) will be in¬ 
stalled in the center of resistance. The 
emplacements can be prepared in the 
trench itself. But it is preferable to 
dispose these weapons in special em¬ 
placements, branched on the approaches. 
The emplacements must be hidden with 
the greatest care to avoid being located 
by the enemy. Each emplacement must 
be completed by shelters for the per¬ 
sonnel and the ammunition. 



The emplacements must be numerous, 
in number superior to that of the bat¬ 
teries available, so as to displace and 
use elsewhere the weapons that may be 
located by the enemy, and in order to 
concentrate on certain points strong 
batteries. 













Field Fortification 


89 


32. Artillery. —There may be allotted 
to the supporting point for its own use 
some field pieces intended for flanking. 
These pieces are always sheltered un¬ 
der casemates. If they utilize uncov¬ 
ered emplacements, the pieces will be 
kept in waiting in bombproof shelter. 
These pieces generally work for the 
benefit of a center of resistance other 
than that in which they are installed; a 
special telephone line must establish the 
necessary communication. 

33. Organized Defense of Intervals. 
—These are zones organized for de¬ 
fense, not much occupied in normal 
times, comprised between two strong or 
supporting points. They must be 
swept by fire and watched carefully. 
These intervals are generally chosen on 
account of the difficulties that the ter¬ 
rain offers for the enemy’s progress by 
reason of natural obstacles (marshes, 
low-lying land, rocky ground). An in¬ 
terval never comprises an empty space. 
It comprises especially: 

(a) A continuous obstacle consisting 
of accessory defenses which will be 
rendered as strong and as impenetrable 
as possible, with passages arranged for 
friendly patrols and attacks. 

( b ) In rear of these defenses, an 
observation approach trench prepared 
as a fire trench, constituting thus with 
the first line trenches strong points 
connected up—a continuous line of 
trenches. The continuous line, in addi¬ 
tion to preventing the enemy from fil¬ 
tering through, removes from the de¬ 
fender the idea of being isolated in his 
strong point. 

In case of attack by the enemy, the 
interval is garrisoned, and the density 
of the defense becomes equal to that of 
the works of the strong points or of 
the neighboring centers of resistance. 


Part IV 

defensive: organization of a sector 

34. A position is constituted by a line 
of supporting points. 

But these supporting points are 
themselves grouped rationally so as to 
constitute sectors each occupied by a 
big unit: Army Corps Sector, Division 
Sector, and, where necessary, Brigade 
Sector. 

The sectors, according to tactical cir¬ 
cumstances and the terrain, may have 
very unequal extents and comprise a 
variable number of supporting points. 

In addition to the work executed in 
the supporting points and in intervals 
between them, the defensive organiza¬ 
tion of a sector will comprise a certain 
number of works of general interest, 
for example: 

(1) Communications (development 
of a good system of routes, installation 
of railroads of 2 feet and 1 foot 8 
inches gauge). 

(2) Shelters for sector reserves 
(natural shelters prepared and im¬ 
proved). 

(3) Emplacements for field and 
heavy artillery (masked, protected: 
the protection may be very great by the 
use of concrete). 

(4) Boom-proof storerooms for am¬ 
munition and explosives. 

(5) Barracks and sheds for men, 
horses and materiel. 

(6) Arrangements of all kinds in 
the rest cantonments. 

The commander of the sector has at 
his disposition sector reserves and artil¬ 
lery, which is assigned to him as his 
own, independently of that which may 
be in his sector, but whose use is re¬ 
served to the higher command. 

A telephonic and telegraph system 





90 


Field Fortification 


well kept up, having its center in the 
command post of the commander of the 
sector, will connect them up: 

(a) Towards the front with the 
commanders of the different supporting 
points of the sector. 

( b ) Laterally with the commanders 
of neighboring sectors. 

(c) To the rear with the higher com¬ 
mand of the organization. 

Part V 

ORGANIZATION OF THE SECOND AND 
THIRD INTRENCHED ZONES 

35. In rear of every intrenched zone 
there must always be established an 
intrenched zone which will be consti¬ 
tuted in an identical fashion to that of 
the first: supporting points organized in 
depth and group in sectors. It must be 
studied and organized, entirely inde¬ 
pendently of the first zone, in the best 
conditions for its own defense. 

The second zone must be stronger 
than the first; its place can be selected 
and studied better, better flanking dis¬ 
positions, the accessory defenses more 
solid and more complete, the shelters 
more carefully constructed. 

The distance from the first to the 
second zone is variable. The latter 
must be chosen in such a manner that 
the enemy, from the same emplace¬ 
ments, cannot prepare an attack simul¬ 
taneously on the first and second posi¬ 
tions. Invisibility must be sought. 
Traces in woods and on counter slopes 
must be used. 

A third zone may be established in 
rear of the second and according to the 
same principles. 

According to circumstances (impor¬ 
tance of a sector, menace of the enemy, 
workers available, materials, etc.) it 


will be organized more or less com¬ 
pletely, or only in its essential details. 

In any case the study of the terrain 
must be made in the greatest detail, so 
as to at once complete the organization 
at the first order. 

Part VI 

distribution of troops 

36. The troops assigned to the de¬ 
fense of a sector are divided in the fol¬ 
lowing fashion: 

(1) On service in the trenches three- 
eighths of the total effective, of which 
two-eights in the fire trenches, one- 
eighth in the support trenches. 

(2) In sub-sector reserve two-eighths 
of the total effective. The troops at 
rest in the shelters or cantonments 
counted in the sub-sector. 

(3) In sector reserve: three-eighths 
of the total effective. The troops at 
rest in the cantonments situated at 4 or 
5 kilometers from the fire trenches. 

37. Troops on Service in the 
Trenches .—These troops have a role 
of advanced posts with reference to 
the troops in rear available. In this 
capacity they must: 

(1) Protect by assuring the solidity 
of the front. 

(2) Get information for and prepare 
the attacks by direct observation, the 
sending out of patrols and the execu¬ 
tion of sudden enterprises. 

By day they have look-outs under 
protected observatories. 

By night, a fraction of a quarter (2 
officers, 4 to 8 look-outs, one squad by 
section) watch and observe in the listen¬ 
ing posts, run out fan shape beyond 
the wire entanglements. 

The rest of the garrison rests, re¬ 
pairs or improves the fortification, 
which must be constantly perfected. 



Field Fortification 


91 


The rapid execution, complete and 
careful, of field fortification involves 
the military honor of the troops in 
charge of it. 

Any chief who tolerates a regiment 
working little or badly, under any pre¬ 
text, is wanting in the first duty of his 
office. 

Part VII 

special, defensive organizations 

38. Blockhouse. — Blockhouses are 
elements of strong points organized so 
as to obtain with a small force a strong 
resistance and good flank fire (Fig. 17). 



Fig. 17.—Plan of the work and accessory 
defenses. 


In their entire make-up, they are gen¬ 
erally constituted by covered trenches, 
with loop-holes for fire and emplace¬ 
ments for machine guns. The roof is 
made by a layer of logs of 0.20 m. 
diameter or railroad rails surmounted 
by a layer of earth which varies with 
the relief allowed. 

The relief of the blockhouse must be 
slight, so as to diminish its visibility, 
unless natural masks hide it. There 
are many types of blockhouse. 

Figs. 17 and 18 represent a block¬ 
house for a squad with machine guns 
on one flank. 

For the details of construction of cov¬ 
ered trenches and of shelter for machine 


guns, see the special chapters, Third 
Lecture. 



Fig. 18.—Plan of blockhouse indicated in the 
arrangement above. 


39. Closed Fire Trenches. —Often it 
may be necessary to fortify in rear of 
the first line a special strong point. If 
there is no ground cover (patches of 
woods, villages, farms, houses, etc.) 
closed fire trenches may be organized 
(Fig. 19). 



Fig. 19.— Plan of an aisle of closed trenches. 


The approach trenches permit the 
circulation between the front and rear 
part of the fire trenches, as well as with 
the exterior. 

Protected shelters and cave shelters 
very largely stocked with provisions 
and ammunition allow prolonging the 
defense to the limit. 


















92 


Field Fortification 


INHABITED PLACES, VILLAGES 

40. Importance .—They constitute im¬ 
portant natural strong positions. Bloody 
episodes of the present war (Vermelles, 
Carency, Souchez, Ablain, Saint-Na- 
zaire, Tahure, Pozieres, Contalmaison, 
Thiepval, Combles, etc.) offer a mask, 
cover, or obstacle, and communications. 

Mask .—Permits concealing the rein¬ 
forcements, especially in flat country. 
The probable force of the defenders is 
unknown. 

Cover .—Against artillery: the first 
houses provoke the burst of projectiles 
and stop the fragments of burst. 

Against infantry: infantry fire is in¬ 
effective against walls 14 inches in 
thickness. 

Obstacle. — To the movement of 
troops, it is difficult to debouch when 
the exits are under hostile fire. 

Communications .—The localities are 
situated at the points of convergence of 
the roads and routes and command the 
lines of communication. 

41. Defensive Organization — Gener¬ 
alities .—Big explosive projectiles have 
considerable effect on villages which 
can be seen from afar. But whatever 
may be the effects in the majority of 
cases, even after a very intense bom¬ 
bardment, parts of the edges of the 
town intact, walls left half stand¬ 
ing, piles of debris which permit 
a fight foot by foot when the enemy is 
too close to continue firing. It is then 
indispensable to provide for the defen¬ 
sive organization of localities, and they 
must not be left out of the line of 
defense. 

This organization must be arranged 
with a view to putting the defending 
troops under shelter from the destruc¬ 
tive effects of projectiles. To this end 
it is necessary to consider several prin¬ 


cipal cases on the subject of the em¬ 
placement of the principal fire crest. 

42. Edges and Approaches Seen 
from Afar and Easily Located by the 
Hostile Artillery .—The village is con¬ 
sidered as a cover or mask, the edge 
prepared as a passive obstacle which 
will be organized only in view of a close 
defense, when the hostile artillery hav¬ 
ing lengthened its fire, it will be possi¬ 
ble to occupy the village. 

The principal fire crest must be es¬ 
tablished forward of the prepared edge 
of the town. 

The exterior edges of the town are 
occupied: hedges, palisades, banks, 
ditches, which are at 50 to 150 meters 
in advance; at the same time, seek an 
open and extended field of fire, utiliz¬ 
ing all the salients for flank fire, either 
by groups of riflemen or well-sheltered 
machine guns. 

43. Edge of Town Defiladed from 
Distant Views (case of a village on a 
counter slope or in bottom of a depres¬ 
sion). Organize the principal fire crest 
on that edge of the town which gives a 
good view and permits a very rapid and 
very solid organization. 

Prolong this fortified edge by en¬ 
trenchments for flank fire on the inter¬ 
vals and cross fire in front of the edge 
of the town; barricade the exits. 

44. Edge of Town at Very Short 
Distance from the Enemy (current 
case in trench warfare). The consid¬ 
erations of the field of fire are the only 
ones of interest. If from the edge of 
the buildings of the town the terrain 
can be well seen to 100 and 150 meters, 
it is organized; if not, the fire line is 
carried forward so as to have better 
views on the enemy’s position. 

As the village can be subjected to an 
accurate and intense bombardment, the 



Field Fortification 


93 


occupants must be protected by solid 
shelters built in the cellars and under¬ 
ground constructions. 

45. Particular Cases. — Where the 
locality has a small front towards the 
enemy (village elongated perpendicular 
to the front). (Fig. 20.) 



Fig. 20.—Village elongated 
perpendicularly. 


Two groups of trenches will be dug 
BB', covering the village. They form 
two bastions, whose curtain will be the 
edge of the village. 

Complete this organization by con¬ 
structing wing trenches VV'. 

Organization of details of protective 
works .—In all cases there must be: 

(1) Clearing off the field of fire: 
burning haystacks, cutting down hedges, 
knocking down walls of enclosures and 
isolated houses. 

(2) Construction of a line of ob¬ 
stacles, extending those which exist 
(iron fencing, walls of enclosures) 
completed by accessory defenses. 

(3) The creation of a principal line 
of fi re% —Organization of walls, hedges, 
houses, entrenchments, sweeping thor¬ 
oughly the line of obstacles and the ter¬ 
rain in front, with shelters for the look¬ 
outs properly reinforced. 


(4) Arrangement for flank fire 
(machine guns enfilading the terrain in 
front of the line of obstacles). Organ¬ 
ization of wing trenches, in echelon, 
somewhat beyond the village to avoid 
the envelopment. To this end, utilize 
the obstacles which are on either side 
of the village, to right and to left 
(walls, farms, patches of woods, ceme¬ 
teries, etc.) or construct new obstacles 
(blockhouses). 

(5) Construction of shelters in rear. 
—Complete utilization of cellars and 
construction of subterranean shelters 
which will complete the system. Gal¬ 
leries will connect the cellars, at any 
rate of the same group. 

(6) Opening of communications, 
or their improvement. — Protected 
paths all along the line of fire. Pas¬ 
sageways through the walls and enclo¬ 
sures. Make the communications al¬ 
ways with a stepped trace and not in a 
straight line in streets enfiladed by en¬ 
emy’s fire. Put up signposts and have 
all the occupants familiar with the com¬ 
munications. Put in pipe system for 
water, if possible, and connect up with 
the wells. 

(7) Organization in the village .— 
During the lulls in artillery bombard¬ 
ment, organize the edge of the build¬ 
ings for close defense, and the supports 
(if the principal crest of fire is in 
front), and if possible a second line in 
the interior. If a water course of a 
large street traverses the village, utilize 
them for this second line; if not, make 
this line in some way. 

(8) Organization of a redoubt, whose 
principal value will be due to its being 
defiladed from’ distant view. Make it, 
therefore, in a solidly constructed 
house, or in an enclosure situated so as 
to sweep, at short range, the exits from 






94 


Field Fortification 


the village. This point will be enclosed 
by systems of accessory defenses. 

(9) If the occupation is prolonged, 
work unceasingly to complete the or¬ 
ganization, so as to be able to make a 
stubborn fight, where necessary, from 
street to street and house to house. To 
this end, prepare an interior division 
into compartments with barricades and 


accessory defenses, which will separate 
portions of the village entrusted each 
to a company, or a constituted fraction, 
each portion forming a strong point. 

(10) Organization of a position in 
rear to prevent the enemy from de¬ 
bouching from the village. To this 
end, construct some elements of trench 
to be occupied by supports, in good 



• 'Comman/cat/no 
1 Treocfi - 


Adjacent strongponet 


• - ■foodnith'kfr, W. 

C —O .. - firing Trenc/t 
■C '' * AtacM/ne (Sun 

...Jy/re fnto/xf/enrent 
Q - • •.. Company CommendAiftr 

Approoc/tTrench I CrasC 

* a/Communication 

• '■•A»embkd >n refern underjhtHtr' 

B - • - Cam party Cam mand Post- 

m ... —- « <• (Catanal) 


“ •' Mouse PemoJiottad 

Fig. 21.— Defensive organization of a large village. 











Field Fortification 


95 


range and in rear of the exits from the 
village. 

(11) Independently of the accessory 
defenses which should envelope the en¬ 
tire village, the lines of access to the 
village on flanks and front must be 
closed by barricades, fixed and mov¬ 
able, except at points which should be 
left free for exterior counter attacks, 
and whose defense will have been spe¬ 
cially organized. 

(12) The judicious employment of 
communications, of barricades, of inte¬ 
rior blocks of buildings, and the com¬ 
plete familiarity with them of the de¬ 
fender give him a marked advantage 
by allowing him to throw his reserves 
rapidly on any point where an enemy, 
who does not know the village, may 
have penetrated. 

(13) Fig. 21 gives an example of 
the organization of a village. 

(14) The hurry order for the con¬ 
struction of defensive works is as fol¬ 
lows: Construct accessory defenses, 
barricades, organization of the line of 
fire, communications, shelters, redoubts, 
interior lines of defense, blocks of 
houses specially prepared (“islets”). 

(15) In the war of movement, such 
an organization, requiring a great deal 
of time, cannot be made. Depending 
on the time available, however, the 
above outlined plan will be approxi¬ 
mated as much as possible. 

46. Barricades. —They will be gener¬ 
ally arranged so as to stop the enemy, 
not only by the obstacle they present, 
but also by the fire of the defenders. 

They serve especially to intercept a 
route of access (road or trench) from 
which one is obliged to follow. 

They may consist of a parapet of 
earth, of sandbags, manure, paving 
stones covered with earth (Fig. 22), or 



Fig. 22.—Barricade of paving stones. 



Fig. 23.—Barricade of barrels and earth. 


barrels (Fig. 23), or may be composed 
by the bodies of carriages whose wheels 
have been removed or immobilized and 
which have been filled with nondescript 
material. 

To permit the use of the road to the 
defender, the barricades are arranged 
in two sections, disposed in echelons, as 
indicated in Fig. 24. 



Barricades may be organized at times 
as simple passive obstacle; for example, 
to close breaches in a wall. 

They are built: 



Fig. 25. 








96 


Field Fortification 


With the trunks of trees disposed 
horizontally, one on top of the other, 
and held by vertical uprights and 
braces (Fig. 25). 

With trees cut down (Fig. 26). 



Fig. 26 . 


With a vehicle, loaded, between the 
wheels of which stumps, fagots, trunks 
of trees, are placed to obstruct the inte¬ 
rior empty space (Fig. 27). 



Fig. 27 . 

They are always placed far in rear 
of the edge of the village and on a line 
with a lateral street to facilitate move¬ 
ment. 

47. Organization of a Cellar— The 
ceilings of cellars, supported by posts, 
will be reinforced with logs, railroad 
rails, sandbags, broken stone, layers of 
concrete, augmenting the thickness of 
the arches and making exploding 
cushions. 

The layers of railroad rails, buried 
in concrete, will be placed on rail 
sleepers passing through the walls of 
the house and resting outside on ma¬ 
sonry pillars. The weight of the layer 
of rails rests, then, on the pillars and 
not on the roof of the cellar. Tacking 
rails, embed in the concrete articles 
of furniture: beds, cupboards, tables, 


chairs; any solid point constitutes a 
center of attraction and resistance for 
the setting of the concrete. 

Assure and protect the ventilation 
carefully. 

Arrange and protect the exits; make 
them double. Connect the cellars with 
each other by subterranean galleries. 
Make loop-holes on a level with the 
ground for machine guns. 

Close hermetically all useless and un¬ 
protected openings, so that the enemy 
cannot throw through them explosives, 
inflammable and asphyxiating matter. 

The crumbling of the house under 
heavy artillery fire only augments the 
protection offered by the caves if the 
precaution has been taken to remove 
from the upper structure all inflam¬ 
mable material. 

Have a stock of tools on hand for 
possible clearing away. Have drinking 
water always on hand, vessels full of 
a solution of hyposulphate of soda and 
Vermorel sprayers to counteract as¬ 
phyxiating gas. 

48. Organization of a House. —Oc¬ 
cupy a house only where it is not sub¬ 
jected to artillery fire. 

Where it is subjected to such fire, 
prepare it but do not occupy it except 
at the moment of the assault. Until that 
moment, find shelter in the cellars or 
hollows of the ground near at hand. 

The houses which are most advan¬ 
tageous for being placed in a state of 
defense are those of two or more 
stories, which have partition walls, fire¬ 
proof roofs, and which have salients 
and re-entrants which allow the foot of 
the walls to be swept by fire; in such 
houses the men are generally behind 
the second or third wall. 

The organization comprises the fol¬ 
lowing operations executed generally by 












Field Fortification 


97 


the different work groups simul¬ 
taneously : 

(1) Remove the roof if it is inflam¬ 
mable, as well as any other useless ob¬ 
ject which may burn; in each room 
place buckets of water or piles of sand 
to extinguish rapidly the beginnings of 
fire. 

(2) Open the interior doors to di¬ 
minish the blast caused by the explosion 
of the projectile. 

(3) Close hermetically the openings 
of the underground room and first 
floor, which must not be used. The 
enemy will not then be able to throw in 
explosives and inflammable materials. 
Barricade the doors with materials of 
big dimensions, those opening inward 
as well as those opening outward; do 
the same for the windows of the first 
floor and arrange in them loop-holes 
(Fig. 28). 

(4) Remove the window shutters of 



Fig. 28.—Window barricaded and provided 
with a loophole. 


the upper stories, close the inside shut¬ 
ter to conceal the defenders, organize 
behind and up to the height of the 
breast a cover one meter thick with 
mattresses, springs, linen, trunks full 
of things, etc.; make loopholes in the 
intervals of the openings; protect the 


riflemen placed behind the first wall 
against stone splinters by the aid of 
mattresses, planks, etc. 

Machine guns level with the ground 
on the first floor. On the upper stories, 
place them at the back of the room. 

(5) In the top story place observa¬ 
tion posts and, where necessary to get 
a dominating fire, some cover for rifle¬ 
men. 

(6) Arrange an exit in case of re¬ 
treat in the face opposite that of the 
probable attack; barricade it, but in 
such a manner as to rapidly free it in 
case of need; make communications 
which permit of easy access to this exit. 

(7) Organize the flanking disposi¬ 
tions for the approaches by occupying 
the salients, making, where necessary, 
trenches at the angles. Place accessory 
defenses completely around the house. 

(8) Fig. 29 gives an example of the 
placing of a two-storied house with cel¬ 
lar in a state of defense. 

49. Organization of Woods. —The 
tactical characteristics are analogous to 
those of villages. Excellent mask 
against sight, even of airplanes. 

Generally, the enemy does not fire at 
♦♦-oops that he does not see. Plence pro¬ 
tection against fire. 

Combats in woods are very difficult 
to conduct. They are like a fight be¬ 
tween blind men. It is especially im¬ 
portant to possess the edge. 

If the topographical situation does 
not permit them to be utilized, they 
must be destroyed. 

50. Defensive Organization of the 
Edges and Approaches of Woods .— 
The occupant of a wood has a clear 
sensation of being under shelter. This 
belief, whether justified or not, un¬ 
questionably gives his nerves a rest. 

On a large wood, the effect of ar- 















98 


Field Fortification 


tillery is very small on account of the 
dispersion of the projectiles. The men 
become quickly accustomed to fighting 
in woods. As they neither see the 
bursts nor smoke of the projectiles, the 
defenders keep their morale. 


of the trench are occupied. Hence very 
ineffectual fire. The principal line of 
fire is organized on the edge if the field 
of fire is sufficient. 

(2) If the development of the edge 
is small (small woods, elongated 




Fig. 29.—Defensive organization of a house with a cellar. 


(1) If the development of the edge 
of the woods reaches 300 to 400 meters, 
the enemy, if he can adjust his fire for 
range, cannot do so for lateral direc¬ 
tion, as. he does not know which parts 


woods), perpendicular to the front and 
easy to locate from afar for the hostile 
artillery, parry the principal line of de¬ 
fense 50 to 80 meters forward and 
organize the edge during the night or 















F i e 1 d][F ortification 


99 


the lulls in the fighting, for the close 
defense. 

51. First Case: Organization of the 
Crest of Fire on the Edge of the 
Woods. —(a) If the field of fire is at 
least 150 to 200 meters, the edge of the 
wood is occupied. The salients, the 
exits, the points for flank fire are or¬ 
ganized without modifying either the 
exterior aspect, or the vertical aspect 
(airplanes). The first line is placed, ac¬ 
cording to the density of the woods, 
from 10 to 30 meters in rear of the 
edge of the woods. The trees and bushes 
are kept on this width, or simply 
stripped on the lower parts to open up 
the view. A line of leafless abatis is 
established (so as not to interfere with 
the firing), which may be interwoven 
with barb wire. 

( b ) In a very thick, dense wood, 
where the clearing up of from 10 to 30 
meters from the edge would necessi¬ 
tate heavy work, put the fire line on the 
edge itself (from 2 to 4 meters; in the 
ditches which one often finds on the 
edges of woods). Create in front at 
100 meters a line of obstacles, wire en¬ 
tanglement, abatis, stretched wire. Be¬ 
hind the strip of woods, which forms 
a mask, make a track of 4 to 6 meters, 
and dig there the trenches. 

On account of the presence of roots 
and of the possibility of defilading the 
relief, the parapet may be raised by an 
additional 2 feet 8 inches to 3 feet 4 
inches, which gives a better field of fire 
over the brush and the abatis. 

It is useful to create in places para¬ 
doses which protect against back bursts 
of projectiles. 

When the terrain is rocky, the roots 
are numerous, the woods very abundant, 
the parapet and the parados may be 
constructed by means of mattresses of 


earth between two layers of poles. 
Sheds may be built, traverses and light 
shelters with the same materials. 



Fig. 30.—Trench in wood, with strong relief. 


52. Second Case: Organization of 
the Crest in Front of the Edge of the 
Woods. —The edge has no field of fire, 
or the wood is narrow and easy to lo¬ 
cate for the hostile artillery. The fire 
line must then be carried forward 50 



to 100 meters. Install on the edge of 
the woods, trenches and abatis for sup¬ 
ports and the close defense, according 
to the same principles as above. 

(a) Trace of the organization on the 
edge of the woods (principal fire line 
of the first case, support line of the sec¬ 
ond case). 

The line of abatis will be organized 
all along the edge of the wood. If time 
is lacking, the abatis is replaced by wire 
wound about and stretched between the 
trees of the edge of the wood. Around 



















100 


Field Fortification 


the elements of trench, passages for 
counter attack will be arranged, care 
being taken to sweep these passages by 
the fire of an element of trench or of a 
machine gun. 

The salients, the debouching points of 
roads, the probable points of passage of 
the enemy, will be first occupied. 

The salients will permit flanking the 
intervals by powerful fire (machine 
guns, when necessary) in front of the 
abatis. If the woods present a straight 
and continuous edge, it will be necessary 
to post in front of the woods, at some 
meters, shelters for machine guns or 
blockhouses, concealed by branches or 
by a very low relief or simply an ele¬ 
ment of tenailled trench so as to permit 
perfect flanking of the edges of the 
woods. 

Progressively, the organization is 
completed by fire crests in the intervals 
themselves, so as to make the front 
impregnable. 

Approaches defiladed, or paths, are 
arranged to connect the shelters with 
the fire trenches. In rear of the possi¬ 
ble lines of approach of the enemy, 
make ambuscades; trenches enfilading 
roads at points where lateral obstacles 
will force the enemy to keep in them. 



Pits for double sentinels are established 
in front of the abatis of the edge of 
the wood. They are connected with 
each other and with the trenches by 
chemins de ronde of 2 or 3 meters, 
straight, so as to permit rapid and easy 
communication (Fig. 32). 

( b ) Organization in zvoods. — Oc¬ 
cupy the natural clear spaces, the big 
gulleys or ravines situated in the in¬ 
terior, to create a crest of fire. The de¬ 
fense of this line is based on the em¬ 
ployment of powerful flank fire, with 
very solid accessory defenses, to make 
up for a very short field of fire. 



Fig. 33.—Defense in woods. 

Cut the line out, if it does not exist, 
being careful to leave enough trees so 
that the vertical aspect of the wood 
does not change (airplanes),but clearing 
away so that the defenders can see the 
enemy for at least 60 meters to their 
front. The trace of the clearing is either 
a straight line; tenailled or stepped 
abatis at the opposite edge make pow¬ 
erful accessory defenses if barb wire 
is woven through them. Make ambus¬ 
cades szvept by machine gilns; nail 
metal trellis to the trees. 

Make passages in echelon for counter 
attacks. Watch the line of obstacles 
from sentinel pits (Fig. 33). 










Field Fortification 


The support lines of organized posi¬ 
tions along the edges of woods are ar¬ 
ranged in the woods upon the same 
principles. 

Fig. 34 gives an example of the or¬ 
ganization of the edges of a wood. 

If the wood is of great dimensions, 


101 


them progressively until the intervals 
attain little by little a degree of solidity 
comparable to that of the centers of 
resistance. 

In the war of movement this plan 
of organizing will be approximated, as 
well as the time available permits. 



Fig. 34.—Defensive organization of the edge of a wood. 


it may comprise from the beginning an 
organization of spaced centers of re¬ 
sistance whose intervals are formed 
almost entirely of accessory defenses. 
But when the two parties are near to¬ 
gether, and when surprises are to be 
feared, it will be necessary, to better 
hold the terrain and because of the 
difficulty of seeing, to create intermedi¬ 
ate strong points and to strengthen 


53. Organization of a Defile. — 
Bridges, fords, roads passing through 
villages, through woods, etc., are con¬ 
sidered as defiles. 

In mountainous country, this terrain 
is reserved for a valley with steep, al¬ 
most inaccessible sides. 

This last is the kind of defile we are 
now going to consider. 

According to the situation, the de- 













1C2 


Field Fortification 


fense may be made in front, in rear, or 
inside of the defile. 

54. Defense in Front. —Purpose: To 
keep the passage of the defile open (ad¬ 
vance guard, rear guard). 

To protect the exit and its vicinity 
from hostile artillery fire. —-The defense 
is made on the arc of a circle so as to 
keep under infantry fire all the posi¬ 
tions favorable to the deployment of 
hostile artillery, on heights dominating 
the exit of the defile. The distance of 
the defense from the line of strong 
points to the opening of the defile varies 
according to the terrain from 3,000 
to 6,000 meters. There are no support 
positions (lack of space), but at the 
entrance there should be a barrier or¬ 
ganized to cover the retreat of the last 
troops (when necessary). 

Very strong zvings. —Defense and 
barricade of all lateral routes, to pre¬ 
vent turning movements. Prepare 
measures of destruction (in a retreat 
march) to block up debouching points. 

55. Defense in Rear. —Purpose: To 
prevent the enemy’s debouching by 
crushing his columns as fast as they 
present themselves. To this end his 
emplacement must be restricted, and 
on this emplacement must be directed 
a concentration of powerful convergent , 
continuous fire. 

Therefore, put the infantry positions 
within good rifle range of the mouth of 
the valley. Place the batteries of ar¬ 
tillery so that they cannot be seen from 
the heights around the defile. 

Positions must be solidly supported 
by flanks on high points. Avoid being 
turned. 

Fig. 35 gives an example of the de¬ 
fense organization of a defile. 

56. Defense on the Inside. —Purpose: 
To complete the defense in front, serve 
as a second line of resistance or as an 


advanced position, hinder the march of 
the enemy by accessory defenses placed 
under an intense fire from the trenches. 
The firing line is placed in rear of the 
obstacles, so as to have a front superior 
to that of the enemy, either by carrying 
the flanks forward and echeloning them 
on the slopes or by occupying a point 
where the defile broadens out (second¬ 
ary valley). 



Establish the trenches on the summit 
of steep slopes on the military crests, 
for they generally have little to fear 
from the hostile artillery. 

Assure the mutual flanking of the 
strong points. Watch out for and guard 
all secondary passages. 

57. Defensive Organization of a 
Stream Crossing. — According to the 
situation, the defense can be made in 
rear or in front. This special organiza¬ 
tion is called “Bridge-head.” 

58. Defense in Rear. — Admissible 
procedure in case of absolute defensive, 
when there are no debouching points on 
the other side of the stream. 








Field Fortification 


103 


Watch along the stream, with mobile 
detachments (with machine guns), 
which occupy elements of trench and 
watch the debouching points across the 
river. Destroy all means of passage 
along a great length. Assemble the 
main body at a certain distance in rear 
so as to bring it rapidly to any point 
where the enemy may be caught in the 
act of passing the stream (Fig. 36). 



Fig. 36.—Defense of a passage in rear. 

59. Defense in Front .—Procedure 
employed to construct a bridge-road. 
The same defensive organization covers 
several points, generally at 300 or 400 
meters apart. A bridge-head should 
satisfy the following conditions: 

(1) Cover the troops in the vicinity 
of the bridge against hostile fire. To 
this end, occupy the heights or emplace¬ 
ments which hold on fire the positions 
favorable for hostile artillery’s bom¬ 
bardment of the bridge. Considering 
the range of heavy cannon and howitz¬ 
ers, it would be well to extend this line 
of supports to 5,000 and even 6,000 
meters from the bridge (Fig. 37). 

(Note. —In the offensive in Picardy, 
the heavy long-range artillery destroyed 



Fig. 37. —Defense of a passage in front. 


points of passage for enemy at 12 and 
15 kilometers.) 

(2) But the troops given the defense 
of the bridge-head are often insufficient. 

The development of the positio^i must 
therefore he in relation to the strength 
of the force defending it. 

The distance of the bridge-head must 
often be as near the bridge as 3,000 
meters. 



Fig. 38. —Bridge¬ 
head in a bend. 

Batteries will be placed on the 
friendly side to support the strong 
points of the wings. 

They must be able to act likewise on 
the interior of the bridge-head. 

(3) Make solid strong points at the 
entrance to each passage. Bridge-heads 
are advantageously placed in the re- 






104 


Field Fortification 


entrant bends of streams. Their de¬ 
fense with two arms against one is then 
easy to obtain (Fig. 38). 

conclusion 

60. Examples of the present war 
abound which prove the strength of re¬ 
sistance of defensive fortifications, 
held by a determined garrison. This 
strength, joined to the power of arma¬ 
ment, is such that it may be said that 
troops which are well commanded, 
which feel themselves well supported, 
which the commander keeps well in¬ 
formed and looks out for, is capable of 
unlimited resistance. Mediocre strong 
points, submitted to frightful bom¬ 
bardments and to furious and repeated 
attacks, have held victoriously, while 
others, better constructed and prepared, 
fell prematurely because the defenders 
had not the necessary confidence il l 
themselves, in their neighbors, or in' 
ultimate triumph. I 

In November of 1914, the Germans 
having made a lodgment at Vigneules- 
Hattonchatel on the heights of the 
Meuse, tried to force the passage of the 
Meuse. A battalion of a French reserve 
regiment, energetically commanded, 
occupied, with one section of machine 
guns, in the Chevaliers Woods (south¬ 
east of Verdun), a defensive organiza¬ 
tion formed of elements of kneeling 
trenches hastily constructed, and hav¬ 
ing in their front only three lines of 
wire concealed at from 30 to 100 yards. 
(The defensive organization of the 
Chevaliers Woods, occupied by a divi¬ 
sion, is given in Fig. 39). 

A night attack was launched by four 
German regiments, commencing at 10 
p. m. and lasting until 4 a. m. the next 
morning. Provided with plentiful am¬ 
munition, the French battalion had in¬ 
structions to hold to the last man. 


The Germans came on in columns of 
fours by the forest paths, yelling, pre¬ 
ceded by flare bombs. 

For six hours the rattle of fire from 
the French trenches was continuous. A 
few Germans reached the French lines 
and were captured. At daybreak the 
four German regiments retreated, leav¬ 
ing 800 men killed and wounded. These 
men lay strewn for the most part over a 
zone between 400 -and 450 meters in 
front of the French trenches. The 
French battalion lost 80 men. 

One thousand men well supplied, well 
officered, energetically commanded, had 
stopped an attack twelve times as strong 
as they. 

Again in November, 1914, at Ypres, 
the French line of attack was stopped at 
300 yards from the enemy trenches, 
from which came a deadly fire. The 
Frenchmen piled into shell-holes and 
old trenches; badly punished, they re¬ 
plied poorly to the fire of the enemy, 
firing into the air and only breaking 
branches over the heads of the 
Bavarians. 

Two French infantrymen succeeded 
in lodging themselves in a hole in front 
of their line. One of them settled him¬ 
self so as to give a flank fire. Without 
changing the aspect of the front of his 
shot-hole toward the enemy, he ar¬ 
ranged a loophole in the side. He then 
waited, commencing his fire when he 
got a target almost to his right. He 
then commenced to shoot from right 
towards the left whenever a head ap¬ 
peared. The Bavarians could not lo¬ 
cate the man. They doubled their fire 
on the French line, then, becoming 
more prudent, took off their helmets 
and only took hasty peeps over the para¬ 
pet. Then they began to shoot high 
and break branches over the heads of 
the French soldiers. 



Field Fortification 


105 


During this time the two French 
sharpshooters, alternating in shooting 
and in improving their hole, had made 
room for two more; these two came 


In front, the fire of the German 
trench appeared silenced; calm settled 
on this part of the battlefield and a 
truce seemed established. 



o 


'Mouse Wire Entanglements 

Con *L .. Woac/s 

Stream , Hills 

Hiring Trench _ _ Hostile Line 

"S. Approoch HCtmmueicat/nf Trench 

Fig. 39. —Defensive organization of the sector Chevaliers Maizey 

of Verdun. 


Woods, southeast 


up, and a trench was commenced. Fi¬ 
nally, when the trench was big enough, 
a noncommissioned officer and fifteen 
men reached it with a rush. 


Toward midday, suddenly the group 
of Frenchmen sprang up; in two rushes 
at full speed over open ground, they 
reached an old abandoned French for- 


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10() 


Field Fortification 


tification 30 meters from the enemy. 
The Germans, surprised, did not fire 
until the last moment; two men were 
wounded. All the rest of the day this 
small group remained there (only one 
man wounded). The Bavarians dared 
not chase them out. 

At night, under the protection of this 
group, the whole company glided for¬ 
ward ; they dug silently, with rifles 
alongside. At daybreak the Germans 
found a trench dug under their very 
noses. 

These two examples, taken from a 
hundred, the thousand episodes of the 


Battle of Verdun, where the develop¬ 
ment of the mechanical power of de¬ 
struction is paralleled by the resisting 
capability of the soldier spirit. 

This spirit, when the last word is 
spoken, will remain superior to the ef¬ 
fects of matter, and confirm this truth 
victoriously announced: 

No inch of ground should be volun¬ 
tarily abandoned, whatever may be the 
circumstances, and troops, even though 
surrounded, must resist to the last man, 
without retreating; the sacrifice on the 
part of each man itself being the con¬ 
dition of victory. 














































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